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Águas Livres Aqueduct

Date of Submission: 31/01/2017
Criteria: (i)(ii)(iv)
Category: Cultural
Submitted by:
Permanent Delegation of Portugal to UNESCO
State, Province or Region:
Ref.: 6221
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The Águas Livres Aqueduct, is a baroque architectural infrastructure commissioned by King Dom João V, which was built between 1731 and 1799,. It is a hydraulic structure that stretches over 36 miles, built of cut stone quarried in the Lisbon area, together with limestone masonry.

It was the last great classical aqueduct to be built all over the world, constituting a system for the capture and transport of water, which passes through five separate municipalities in Portugal: Amadora, Lisboa, Odivelas, Oeiras and Sintra. It begins in a rural area, in the municipality of Sintra, where it cohabits with cultivated fields and pine groves, and, throughout its length, it crosses urban areas, surrounded by buildings and public roads. In the municipality of Amadora, it runs parallel to the railway line from Sintra to Lisbon.

On the one hand, the Águas Livres Aqueduct is characterised by its main section, known as the Main Aqueduct, which stretches over a distance of 14.256 km, and by a series of subsidiary aqueducts and head race tunnels that, together with the main section, comprise a total network of roughly 58 km. Over the course of the Águas Livres Aqueduct, the water is transported through the action of gravity (roughly 3mm of water for each metre), sometimes running underground, and at other times breaking out onto the surface. At its extremities, it has three main reservoirs: two catchment areas, in the municipality of Sintra and in the municipality of Amadora, known respectively as the Mãe de Água Velha (Old Reservoir) and the Mãe de Água Nova (New Reservoir), as well as a reservoir in Lisbon, known as the Mãe de Água das Amoreiras (Amoreiras Reservoir).

The Main Aqueduct, which begins at the Mãe de Água Velha, in the municipality of Sintra, and ends in the area of Amoreiras, in the parish of Santo António, in Lisbon, was fed by 58 separate water sources.

The visible stretches of the aqueduct display a structure built of limestone blocks, with rows of regular and even-sized cut stones, designed to support the water conduits, which, in turn, are protected by walls of stone pitching with filled joints, with a round, flat or angular roof, interrupted by vents or skylights, when the structure runs underground. These vents or skylights provide the lighting for the water conduits and head race tunnels, as well as ensuring that they are supplied with oxygen, in order to guarantee the safe quality of the water and to allow for the continued presence there of human beings to clean the gutters and supervise the structure.

In the section of the aqueduct that is visible over the Alcântara valley, in Lisbon, these vents or skylights are more elaborate, displaying erudite architectural elements, such as pilasters and pediments.

The idea of capturing the free waters (Águas Livres) for the aqueduct dates back to the time when there was an insufficient water supply within the city of Lisbon, particularly in the western area, in Bairro Alto, where the problem was further exacerbated by the urban growth that took place in the late sixteenth century. This situation became even worse in the reign of Dom João V. Accordingly, on 12 May, 1731, the King of Portugal ordered the beginning of the Águas Livres Aqueduct construction.

The building of this public work took on special significance for the Municipal Council and for the people of Lisbon, since they were both called upon to bear the brunt of the costs of this work. The tax that the local population had to pay for this purpose, known as the Real D’Água, dates back to 1729, and was levied on staple foodstuffs, such as wine, meat and olive-oil.

The building of the Águas Livres Aqueduct was completed in 1799, and, in 1834, the Mãe d’Água reservoir in Amoreiras was finally ready for use. Besides its being one of the most splendid of the many monuments that the king ordered to be built or had planned for the city, the fact that the Águas Livres Aqueduct did not suffer any major damage with the devastating earthquake that struck Lisbon in 1755 also contributed to the national and international recognition of its solidity and of the technical prowess demonstrated by Portuguese military engineering.

The construction of the Águas Livres Aqueduct was an extremely lengthy process, taking all of the eighteenth century and continuing well into the nineteenth century, with the building of its secondary branches – subsidiary aqueducts, water conduits and head race tunnels – and its fountains, as well as, finally, the completion of the Mãe de Água reservoir in Amoreiras.

The various stretches that were built are the result of the work planned by the different people responsible for overseeing the aqueduct’s construction, the most notable of whom were the Portuguese military engineers Manuel da Maia (1732-1736) and Custódio Vieira (1736-1744), as well as the Hungarian military architect Carlos Mardel (1746-1763). Although there were several different people involved in the design of this work, it should be stressed that it maintained a great conceptual unity.

The most important areas, namely the reservoirs, the skylights and the section of the Main Aqueduct, in the area of Amoreiras, in Lisbon, are notable for the different ways in which their construction was monitored and developed during the various phases of their design and construction, namely at the level of the most erudite treatments that they were afforded and the extreme care that was taken over their decoration.

The process involved in the conception of the work of the Águas Livres Aqueduct, allied to the quality of its construction and the great dimension and reach of the water supply system that it entailed, are all evidence of the singular role that this hydraulic structure has played in the context of world architecture.

In order to underline the singularity of this work, it is essential to mention that the construction of this aqueduct displays architectural and structural solutions that were highly innovative for its time, as, for example, the construction of galleries with a height adapted to the human scale, a feature that, on the one hand, facilitated its maintenance, while, on the other hand, made it possible to undertake building and repair works inside the gallery without needing to interrupt the supply of water.

The Águas Livres Aqueduct is composed of various sections at the surface which, most of the time, follow the route taken by the former Roman aqueduct. The section at the surface that is most eye-catching and impressive is the stretch that crosses over the valley of the Ribeira de Alcântara, in Lisbon, standing on a row of different-sized pointed arches. The dimensions of the area that this section crosses did not leave much room for adopting a different technical solution.

The arches of the Alcântara valley, in Lisbon, consist of a row of pointed arches supported by pillars made of blocks of cut stone. This whole section was surmounted by classically inspired lantern-shaped skylights, made from blocks of ashlar masonry, with hipped roofs. The skylights have a pinnacle at their uppermost point and stand upon triangular pediments, with Tuscan pilasters in the corners, wider at the bases and standing on pedestals, surmounted by a frieze and a cornice, displaying a semi-circular arch on each face, standing on prominent imposts and with an equally prominent keystone.

This group of arches differs from those existing on the other stretches of the aqueduct, since these latter structures have a square floor plan, with a hipped roof, and contain four right-angled windows, protected by railings.

Throughout its course, the hydraulic structure has multiple skylights, either plain or afforded an artistic decoration, with attention being drawn to the fact that some of them have a baroque inspiration, with a domed roof, crowned by pinnacles surmounted by a sphere.

Both the Arco das Amoreiras and the Arco de São Bento, two arches located in Lisbon, are characterised by their sober lines, displaying a geometrical composition, in keeping with a neoclassical context, which makes it easy to associate them with the triumphal Roman arches, and, at the same time, they are adorned with baroque decorative elements.

The Águas Livres Aqueduct ends in a reservoir – the Mãe d’Água das Amoreiras – which was not planned to be merely utilitarian in nature, so that, even through its geographical location, it has been afforded an artistic appearance that makes it a grandiose and clearly visible building.

The building housing the reservoir of Mãe d’Água das Amoreiras (in the parish of Santo António, in the municipality of Lisbon) displays mostly sober architectural lines. Attention is drawn to some of its classical features, such as the use of the Tuscan order, and its decorative features, such as the gargoyles in the cornice. All of the building’s façades, when compared with those of the rest of the area in which they are to be found, have very small doors and windows.

Justification of Outstanding Universal Value

The Águas Livres Aqueduct is identified as a hydraulic structure that has two quite distinct aspects: a rural aspect, where technique outweighs architecture, directed by Portuguese military engineering and based on the architectural treatise of the Roman Vitruvius – De Architectura Libri Decem – and an urban aspect, where architecture outweighs technique, in this case being based on the treatise of the Renaissance architect Sebastiano Serlio.

In 1719, the king of Portugal, Dom João V, brought over from Italy one of the leading exponents in architecture of his generation, Filipo Juvarra. It was his intention to plan a new royal palace and a Patriarchal Church whose grandeur would serve to enhance the image of his personal power and royal magnificence. It was precisely within the context of Juvarra’s sketches for this new complex designed for the king that the idea arose of building the Aqueduto das Águas Livres, which would form the basis for the modernisation of Lisbon’s western region.

The responsibility for designing the most significant works of the period of Dom João’s reign was handed to foreign specialists, and this hydraulic structure was included in this group. Several foreigners were involved in the design of this aqueduct, working there as architects: António Cannevari, Carlos Mardel, João Frederico Ludovice, Miguel Ângelo Blasco and Theresio Micheloti, as well as other surveyors and master stonemasons.

The eclectic component, which is so evident in this complex hydraulic system, meant that the Águas Livres Aqueduct was able to display a set of values that are intrinsic to it and which should be highlighted because of their multidisciplinary richness and their original way of presenting a work that combines service, technology and architecture: 

  1. Archaeological value: this aqueduct permits a comparison with the former aqueduct of Olissipo (third to fifth century AD), visible, among other sources, in the following references:
  • First half of the eighteenth century, História Jurídico Panegirica do Magnífico Aqueducto das Águas Livres (an unpublished copy at the Library of Rio de Janeiro), by Inácio Barbosa Machado, written at the time of the building works of the Águas Livres Aqueduct, whose path runs parallel to the former aqueduct, with traces of the earlier structure being found until Amadora;
  • Considerações by Manuel da Maia, where there are references to the existence of the aqueduct of Olissipo and the building materials used.
  • Nineteenth century, A Memória sobre as Aguas de Lisboa (1895), by Augusto Pinto de Miranda Montenegro, refers to the existence of the remains of former constructions that point to the earlier construction of an aqueduct here;
  • Nineteenth century, Carlos Ribeiro, a geologist, identified the aqueduct of Olissipo in his report published in 1879, in the Revista das Obras Públicas, and also in his Memória sobre o abastecimento de Lisboa, com águas de nascente e águas de rio. (LARCHER, 1937, p. 9);
  • Twentieth century, Jorge das Neves Larcher, in his Memória Histórica Sobre o Abastecimento de Água a Lisboa até ao reinado de D. João V (1937), highlighted the possible course followed by the former aqueduct based on the discovery of its remains;
  • Fernando de Almeida in his Nota sobre a barragem romana de Lisboa (1968) also referred to the existence of the aqueduct of Olissipo.

2. Documentary value: A monument that was built before the 1755 earthquake in Lisbon, which still preserves most of its documentary sources, such as, for example, the crossing of the Alcântara valley, the most visible and expressive aspect of the Águas Livres Aqueduct, completed in 1744, with the placement of the keystone in the highest arch.

3. Industrial value: It represents the first stage in the history of Lisbon’s water supply, which was characterised by the transport of water through mainly stone structures, under the action of gravity.

4. Technical value: It permits an analysis of the evolution of an eighteenth-century system, whose transformations in the nineteenth century (for example, the introduction of iron pipes, siphons, the construction of water treatment stations and steam-powered pumping stations) allowed for its continued use until the end of the 1960s.

5. Social value: The role that water played at the time as an element of recreation and conviviality, both on the part of the people who used the aqueduct crossing the Alcântara valley as a point for entering and/or leaving Lisbon (with attention being drawn to the event that took place between 1836 and 1839, related to the probable crimes committed by Diogo Alves, which, still today, are intrinsically linked to the structure’s social history) and on the part of the nobility, who used the reservoir of Mãe d’Agua das Amoreiras as a place for festivities, an example of this being the wedding celebrations of Dom Luís I.

6. Ethnographic value: A monument that functions as a repository for the collective memories of the city of Lisbon, guaranteeing, as a legacy, the maintenance of its identity for future generations.

7. Historical value: A testimony to the city’s evolution over various periods. Its importance in the context of Lisbon’s urban development over the eighteenth century makes the Aqueduct a crucial reference in Lisbon’s urban landscape.

8. Cultural and educational value: As a museum monument, it provides important scientific knowledge, making it possible to develop cultural programmes aimed at different audiences, supporting their training and developing research projects in various areas.

9. Environmental value: It represents a fundamental tool in the management of water resources and emphasises the role of water as a universal good. In a symbolic way, it also highlights the importance of ecosystems.

Criterion (i): The Águas Livres Aqueduct is an exemplary piece of architecture, which includes the world’s largest pointed stone arch with a height of 65 metres and a width of 29 metres. It was the last classical aqueduct to be built anywhere in the world, constituting an example of the perfect fusion between classical architecture and the technical knowledge that characterised Portuguese military engineering and made it possible to cross over the seismic fault of the Alcântara valley, in Lisbon, as well as the great chasm that still exists there over a length of 941 metres, and even to survive the earthquake of 1755 (…).

The Águas Livres Aqueduct displays yet other factors that mark the originality of its construction, such as the continued presence of the stones that supported the scaffolding and the existence of two footpaths that were used, until 1852, by people and animals entering and leaving the city of Lisbon (Ponte dos Arcos).

Criterion (ii): The system of the Águas Livres Aqueduct is the result of an important blending together of knowledge from Classical Antiquity, the European Renaissance and eighteenth-century technology.

This hydraulic work includes two distinct aspects: a rural aspect, where technique outweighs architecture, with the work being directed by Portuguese military engineers based on the architectural treatise of the Roman Vitruvius – De Architectura Libri Decem – and an urban aspect, where architecture outweighs technique, in this case being based on the treatise of the Renaissance architect Sebastiano Serlio.

In Lisbon, the Águas Livres Aqueduct adopted bolder and more innovative solutions, such as recovering the use of the Gothic arch and the principle of communicating vessels, resorting to fountain pipes, the precursors of the present-day siphons.

Criterion (iv): The stylistic eclecticism that the baroque movement fostered all over Europe in the eighteenth century, as well as the spirit of discovery, adventure and migration, was expressed in the phenomenon of a widespread migration of artists, which necessarily affected Portugal, too. The work for the building of the Águas Livres Aqueduct was directed by several different engineers who worked there as surveyors, measurers, stone masons and architects, as was the case with António Cannevari, Carlos Mardel, João Frederico Ludovice, Miguel Ângelo Blasco and Theresio Micheloti.

Despite the eclecticism that such movements gave rise to, the national characteristics for the production of buildings inevitably imposed themselves, making it possible to underline the existence of an eighteenth-century Portuguese baroque style, relatively belated in terms of the European movement and marked by its profoundly national roots, which, in turn, gave rise to a Brazilian colonial baroque style, clearly evident in the construction of the Aqueduto do Carioca and its respective fountain, in the city of Rio de Janeiro, in Brazil.

Statements of authenticity and/or integrity

The hydraulic structure remained fully operational until the late 1960s, which meant that it underwent some changes of a technical nature, although these have not affected the integrity of the monument.

The fact that, over a length of twelve kilometres, the aqueduct ran through an urban environment meant that, at certain periods, decisions had to be taken that gave priority to the growth of the city and which necessarily called for some alterations and cuts in its structure. However, the cuts that were made did not detract in any way from the characteristics of the aqueduct itself.

At the same time, in order to ensure the protection and safeguarding of the monument, the structure has been subjected to a number of interventions that have respected the original techniques and materials used in its construction, in full compliance with the law, and that have taken nothing away from the monument’s integrity.

The Águas Livres Aqueduct was classified as a National Monument, also comprising the reservoir of Mãe d’Água das Amoreiras, through the Decree of 16 June, 1910, published in the Diário do Governo, 1st series, No. 136, of 23 June, 1910. In 2002, this classification was extended to cover the whole of its length, its branches and other related parts, through Decree No. 5/2002, published in the Diario da República, 1st series – B, No. 42, of 19 February, 2002.

This classification as a National Monument guarantees the aqueduct a Special Protection Area, of 50 metres throughout its whole extension, which guarantees its safeguarding. 

Comparison with other similar properties

Portugal has an important heritage in terms of hydraulic structures for the transport of water, built, above all, from the late Middle Ages onwards, when the increase and development of its urban centres led to a shortage in the supply of water that the existing structures, dating from the time of the Roman occupation and intended to supply both agricultural and human needs, could no longer meet.

Aqueduto de Água de Prata (Évora)

This hydraulic system, built between 1531 and 1537, is considered to be one of the most important public works undertaken in Évora in the first half of the sixteenth century. Inaugurated on 28 March, 1537, it was further extended until the end of the sixteenth century through the building of fountains in some of the city’s squares.

Built under the direction of the royal architect, Francisco de Arruda, the work extends over a length of 18.3 kilometres. It took only six years to build, most probably being erected over the former Roman aqueduct that existed there.

The Aqueduto da Água de Prata was built completely of stone masonry. It begins at the springs of Graça do Divor and ends in the late medieval wall, at the entrance to the city.

Together with the fountains for the supply of public water, the reservoir of Rua Nova and the volumes of the houses built between the arches of the aqueduct, the architectural profile of the Aqueduto da Água de Prata helps to give Évora a curious and monumental appearance in urban terms.

Aqueduto da Amoreira (Elvas)

 The experience of Évora, the first large Iberian city to have had an abundant supply of running water since ancient times, stimulated the building of other aqueducts in the region. Among these, the Aqueduto da Amoreira in Elvas is particularly noteworthy.

In the fifteenth century, the existence of just one single well (funded by the local population) to supply the city’s needs in terms of water proved to be insufficient for its roughly 9,000 inhabitants. In 1529, prospecting and some building work were undertaken at the springs of Amoreira, located a few kilometres from the city, and, in 1537, the architect Francisco de Arruda came to Elvas and work started on the building of the aqueduct. However, it was not until 1622 that water began to flow from the fountain built in Largo da Misericórdia, in Elvas. From here, it was carried to other fountains, which, like the first one, have since been destroyed, moved or replaced.

The 843 arches built in stone and mortar, which make up the Aqueduto da Amoreira, result from a process that, on the one hand, involved the participation of various architects in a number of interventions, all of whom made different formal decisions and came from varied technical backgrounds. On the other hand, the aqueduct’s construction was marked by various events that required a number of campaigns of building work in order to strengthen the structure and undertake profound repairs.

In 2012, the Aqueduto da Amoreira was inscribed in the World Heritage List, as part of the Garrison Border Town of Elvas and its Fortifications.

Aqueduct of Padre Tembleque (Mexico)

The Aqueduct of Padre Tembleque was built between 1555 and 1572 and consists of a hydraulic system located between the states of Mexico and Hidalgo, on the Central Mexican Plateau.

This hydraulic system is composed of a water catchment area, springs, main and secondary branches, distribution tanks, arcaded aqueduct bridges, reservoirs and other auxiliary features, which stretch over a maximum distance of 48.22 kilometres 

In keeping with the traditional Mesoamerican construction techniques, the aqueduct’s structures were built of adobe. However, at the same time, they also reference some European models of water conduction developed during the Roman era.

Along its 48 kilometres’ extent, this hydraulic system integrates impressive architectural structures, such as the arcaded aqueduct of Tepeyahualco, which reaches a total height of 39.65m, including the central arch, which is 33.84m high.

The aqueduct was built by Franciscan friars with support from the local communities, resulting in a unique hydraulic system that is a skilful representation of the ingenious fusion of Mesoamerican and European construction traditions, combining the local mestizo tradition with the tradition of Roman hydraulics.

The system is exceptionally well-preserved and some areas still remain operational today. 

The Aqueduct of Padre Tembleque Hydraulic System was inscribed in the World Heritage List in 2015.

Aqueduct of Segovia (Spain) 

The Roman Aqueduct of Segovia, which dates from c. 50 BC, is a construction consisting of two tiers of arches and forms part of the historic city of Segovia.

The hydraulic structure is built of masonry, 813 metres in length, consisting of four straight segments and two superimposed arcades borne by 128 pillars. At the lowest point of the valley, the Aqueduct stands at a height of 28.5 metres above ground.

The Aqueduct of Segovia is the best known of these civil engineering feats due to its monumentality, its excellent state of conservation, and, in particular, its stunning location in relation to the urban site.

The Old Town of Segovia and its Aqueduct was inscribed in the World Heritage List in 1985.

Aqueduct of Tarragona (Spain)

This is a Roman aqueduct, built over the Barranco dos Arcos, which carried water from the River Fancolí to the old city of Tarraco (present-day Tarragona).

Built in the first century, in the reign of the Emperor Augustus, its construction coincided with the growth of the city, the capital of the Roman province of Hispania Citerior Tarraconensis.

The bridge has a length of 217 metres, which does not include the gallery along which the water was conducted. This was roughly two metres high and has since disappeared. This aqueduct has two tiers of superimposed arcades, with eleven arches on the lower level and twenty-five arches on the upper level. The arches, which are 6.30 metres wide, 5.70 metres high and 1.86 metres thick, are placed at a distance of eight metres from one another.

On the northern side, the aqueduct is 56.8 metres high and, on the southern side, it is 56.4 metres high.

Aqueduct of Pont-Du-Gard (France)

The Pont du Gard was built by the Romans shortly before the Christian era, and, at a height of 49 metres, is the world’s highest Roman aqueduct.

The hydraulic structure, which transported water under pressure for five centuries, fed the city of Nîmes, in France. It is composed of three tiers of arches superimposed on one another, consisting of six arches in the first row, eleven arches in the second row and forty-seven arches in the top row. This arrangement of arches was a very rare construction for its time and is now the only example of an aqueduct of this type that is still visible today.

It is estimated that more than a thousand men worked for five years on its construction. 

Its current state of conservation is quite remarkable and allows us to easily see that this is a masterpiece of the human creative genius.

Aqueduto das Águas Livres, Lisbon: comparison

As far as the aqueducts of Segovia, Tarragona and Pont-du-Gard are concerned, we should highlight the decisions that were taken to cross very deep valleys and the need to find suitable solutions for each case. So, in order to overcome the Alcântara valley, in Lisbon, whose maximum height is more than 60 metres, Custódio Vieira, a military engineer, was forced to go beyond the treatises existing at that time, which provided for the building of tiers of arches placed on top of one another, and instead build for the Águas Livres Aqueduct a row of 35 arches over a distance of 941 metres, where just one of the (pointed) arches reaches a height of 65 metres. In the case of the Pont-du-Gard aqueduct, in France, the tallest arch is less than 50 metres in height, so that, for this reason, the aqueduct consists of three superimposed tiers.

In the case of the large aqueducts of the Iberian Peninsula, Segovia and Tarragona, although these do not even reach a height of 30 metres, they also adopted the solution of building two tiers. We can therefore conclude that the Águas Livres Aqueduct goes much further than all the other known examples in terms of the solutions that were adopted. 

As far as the aqueduct of Padre Tembleque, in Mexico, is concerned, if we assume that both the complexity of the system and the human efforts that went into its construction are important contributions to its exceptional universal value, together with all the characteristics of this hydraulic system, and that the springs, main and secondary branches, distribution tanks, arcaded aqueduct bridges, reservoirs and other auxiliary features are also qualities that help it to achieve this degree of exceptionality, then it is important to stress that in the Águas Livres Aqueduct we find the same attributes taken to the highest possible level plus an exchange of technical knowledge that together permit us to describe this construction as exceptional. The techniques that were used in its construction and the cultural exchanges that took place are particularly visible in the masterful work of the monumental row of arches over the Alcântara valley, in Lisbon, and the water cathedral that is represented by the reservoir of Mãe de Água das Amoreiras.