The ever increasing complexity of densely built-up areas, including above and below surface infrastructures, requires a proper registration of the legal status (private and public). This can only be provided to a limited extent by the existing two dimensional cadastral registrations. The possibility to register property in three dimensions efficiently will facilitate the dense and complex use of space. Despite all research and progress during the last decade, still no country in the world has a true 3D cadastre, the functionality is always limited in some manner; e.g. only registering of volumetric parcels in the public registers, but not included in a 3D cadastral map, or limited to a specific type of object with ad hoc semi-3D solutions (e.g. for buildings or infrastructures). The aim of the Workshop on 3D Cadastres is to consider the 3D issue of cadastral registration in an international context.