One of the significant challenges in current 2D Land Administration Systems (LAS) is defining and registering the Rights, Restrictions and Responsibilities (RRRs) attached to the underground objects. A 3D LAS can facilitate a better understanding, as well as a more efficient registration and clear visualisation of the RRRs than a 2D LAS, through 3D digital modelling of the legal ownership of underground objects below the surface. To register the objects below the surface in a 3D LAS, 3D physical data as well as 3D legal data shall either be registered and integrated into one model, or the physical and legal models shall be linked effectively. In the context of this paper, the IFC (ISO 16739:2018) is used to register the 3D physical data, while the Land Administration Domain Model (LADM, ISO 19152:2012) is used to structure the legal data. To achieve the link of the respective legal and physical data, the classes of the LADM are mapped to the elements of the IFC. A standardised workflow is presented in this paper where the inclusion of the legal, organisational and technical aspects of modelling the legal ownership results in a comprehensive approach to solve the challenges that currently prevent the registration of the RRRs of 3D objects below the surface in LASs. This paper also provides a general method for mapping the LADM classes to the IFC entities. Two case studies were conducted to assess the technical aspect of the workflow, where the RRRs of objects below the surface and the parcels above the surface were registered and visualised on the 3D geospatial visualisation platform CesiumJS.