The building comprises a 200 metre tall tower and 20 metre deep basement in a densely developed urban area. The tower has a steel frame closed by glass panels. The vertical loads are transmitted to the ground by six mega-columns and by a core in the central area. The lateral load restraint is provided by a permanent slab placed according to the top-down method. This paper discusses the geotechnical issues associated with the project and the ground investigation carried out to assess both the variability of the underlying soils and the parameters for design. The large amount of information on ground conditions around the site at shallow depths was integrated with a site-specific investigation that reached depths of 80 metres. Soil parameters were extrapolated from cross-hole tests, which were carried out with two boreholes and from the measurements of the mechanical energy, pressures and torque (PAPERO tests) during drilling. The groundwater water level was found at approximately 20 metres depth. The information provided by the ground investigation allowed the design of the retaining wall and the foundation system and the selection of a construction technique that accounted for the urban context.