The island of Gaddtarmen (Hauensuoli) off Hango (Hanko)
forms a natural harbour on a sailing route in the east-west direction. Sailors have made more than 400 carvings on the rocks while awaiting favourable winds. The oldest drawings date from the 15th and 16th centuries. Most of the carvings decpict coats of arms of Swedish and Finnish gentry. The site is a unique document relating to the history of the Baltic Sea.Hauensuoli (r. Gaddtarmen - "Pike Gut") is a strait between two small islets off Hankoniemi Cape, the southernmost tip of the Finnish mainland. The property is located in the City of Hanko. Owing to land uplift, the strait is now only 10-15 metres wider, but it was originally wider and navigable. The islets are outcrops of granite worn smooth by the continental ice sheet and the action of the Baltic Sea.
Throughout history, Hankoniemi Cape has been an important halting place for seafarers in the Gulf of Finland, being already mentioned in the Early Middle Ages in the so¬called Danish Itinerary of sailing routes in the Baltic. The oldest engraved markings at Hauensuoli date from the 15th century and in the following century it was famed for its sheltered harbour and rock drawings, being mentioned in Olaus Magnus's "Historia de gentibus septentrionalibus" (1555) among other works. The site is mentioned by later historians and travellers from the 17th century onwards.
The rock drawing area at Hauensuoli encompasses roughly three hectares on the two islands with over 600 drawings, mostly from the 16th and 17th centuries. There is a wide range of drawings and markings. Waiting for the right wind, many people would occupy themselves by engraving their initials or heraldic devices on the rocks to
commemorate their visit to the site. This unique "guest book" of the coast of the Gulf of Finland reflects the history of the region.
Three shipwrecks have been discovered in the immediate vicinity of Hauensuoli with well preserved structures. To the north of the strait lies a shipwreck less than 20 metres in length, which was investigated in the 1970s. It was carrying a cargo of 17th-century Dutch ornamental tiles, among other items. To the south is an undated wreck approximately 20 metres long, and to the east of the strait is an uninvestigated wreck roughly 30 metres in length.
The underwater heritage of the vicinity of the natural harbour at Hauensuoli provides an added element to understanding the significance of the property. Organic material, such as wooden wrecks are preserved well in the waters of the Baltic Sea with their low salinity. Old shipwrecks are officially classed as antiquities according to Finnish law.
The rock drawing site at Hauensuoli and its surrounding underwater cultural heritage are a unique culture-historical monument among the harbours and anchorages of the Baltic. Drawings and markings engraved on its shores for over half a millennium point to its maritime significance as a resting place on an ancient sailing route. The drawings are also a unique historical document partly connected to documentary sources and the overall history of Northern Europe. Hauensuoli also has an impressive location in a narrow archipelago zone between the mainland and the open sea.
The rock drawing area and the wrecks are protected under the provisions of Finland's Antiquities Act. The National Board of Antiquities, the City of Hanko and the land owner, the National Board of Forestry are jointly responsible for the conservation of the property. The drawings have been cleaned at intervals of a few years. A new project for the documentation of the property is being planned and a tentative research and care plan has been drawn up for the area. During the summer season there is a regular ferry service to the islands from Hanko.