The slope stability analysis for MSW landfills is usually performed using conventional method of slices or translational wedge method considering potential failure surfaces at limit equilibrium. The safety factor is then determined by comparing the sum of the resisting forces to the driving forces, mobilized along the potential failure surfaces. Usually a safety factor of 1.5 is considered acceptable, other specific values can also be mandated by regulation. It is however uncertain whether or not conventional limit equilibrium methods are applicable to MSW because of their ability to undergo large strains without reaching failure. This paper presents a case study concerning the stability analysis of the Warsaw old town Gnojna Grora hill. The problem of its stability has its roots in the 17th century when Gnojna Grora was used as a municipal landfill. The paper describes its historical background, and the engineering analysis carried out to verify its stability. The paper shows that there is a high risk of failure of the old town hill if the hydraulic conditions change.