This paper presents the design, construction and back analysis of the basement retaining wall of a major commercial development in Bogota, Colombia. The development consists of 4 eleven-story office towers, and 4 basements for car parking use, occupying the entire venue area (18,000 m² per basement). A permanent structural diaphragm wall allowing the construction of the slabs in a Top-Down sequence was designed for a maximum depth of excavation of 15.0m. The ground profile mainly consists of very soft clay with natural water content up to 200%. An important number of in-situ shear vane tests and laboratory tests were performed as part of an additional ground investigation in order to have more accuracy in the undrained shear strength of the clays. The project is heavily instrumented with inclinometers, piezometers, extensometers and topographical survey. The excavation is complete and the theoretical results obtained during the design stage are compared with the instrumentation measurements. This back analysis was used in the form of adjusted sets of soil parameters for traditional elasto-plastic modelling and finite element modelling of the excavation sequence.