Using advanced hydrogeological and geomechanical finite element modelling, it has been possible to model the mechanical behaviour of a large slope movement, the Triesenberg landslide. This slope is located along the Rhine valley in the Principality of Liechtenstein, covering an area of around 5 km2 which includes two villages. Pore water pressure fields calculated by the hydrogeological model were used as input for the geomechanical model. The results obtained through numerical simulation agree fairly well with field measurements of peak velocity, spatial and temporal distribution of velocity and total displacements. Such results were obtained using a Modified Cam-Clay elasto-plastic constitutive model for which the required material parameters were obtained through careful geotechnical tests. These finite element models were carried out in 2 and 3 dimensions in order gradually to improve the understanding of the physical phenomena governing the hydrogeological conditions and the movements of the slope.