The first joint STAB/ICOMOS Advisory Mission to a World Heritage property was carried out within the framework of the World Heritage Convention and the Convention on the Protection of the Underwater Cultural Heritage.

The World Heritage property "Ancient City of Nessebar" (Bulgaria) hosted an Advisory Mission invited by the Bulgarian authorities and carried out jointly by experts of the UNESCO Scientific and Technical Advisory Body (STAB) to the Convention on the Protection of the Underwater Cultural Heritage and ICOMOS International (Advisory Body to the World Heritage Committee). The mission experts assessed the state of conservation of the property, including the underwater archaeological remains, and provided capacity building for Bulgarian experts in coastal management and in the preparation of Heritage Impact Assessments for World Heritage properties. The mission took place from 28 November to 3 December 2017.

The mission experts examined existing and proposed projects and developments within the boundaries of the Ancient City of Nessebar and its buffer zone, including in the territorial waters of the peninsula, and provided preliminary insights on the scope of analysis needed to assess their impacts.

The STAB experts conducted an underwater survey of archaeological remains and provided recommendations for additional research that may be needed to appraise the archaeological potential of the submerged setting of Nessebar and assess measures to be undertaken to minimize impacts on the submerged remains, in line with Article 5 of the 2001 Convention.

The state of conservation of the property will be examined by the World Heritage Committee at its 43rd session in 2019.