The deep excavation in built-up urban areas with buildings and streets surrounding the site makes them quite formidable problems. Such a project of eight storey administrative-residential building located in the city centre of Tirana, Albania has been carefully analyzed. The project anticipates a 20.5m deep excavation to be carried out with six underground storeys. The task becomes even more demanding having in mind the fact that the site is surrounded with six and eight storey buildings with basements. The deep excavation pit with dimensions 27.7 × 36.9m is secured by a multi anchored diaphragm wall. The retaining system as a temporary support has to ensure the stability of the soil and enable undisturbed excavation. The diaphragm wall has been analyzed in several phases using the finite element method to obtain the shear, moments, displacements and support reactions under earth and water pressure on different levels. In this paper the numerical modelling of the 20.5m deep excavation is presented with some conclusive discussions.