The Cathedral of Vilnius is one of the main architectural monuments in Lithuania. This structure was built in unfavourable geological conditions. Due to this reason, the foundation of the building subsides; there occur wall deformations and cracks. Preservation of the building is today’s urgent problem. When evaluating the geologic environment from the perspective of engineering, construction works require deep analysis of the following key environment components and discuss them: relief, soils of geologic structure and their geotechnical properties, conditions of underground water occurrence and geological processes, and condition of the foundation. The article provides the brief history of construction and reconstruction of the Cathedral based on archival studies, the description of engineering geological conditions, and the archeologic and historic material of the evaluation of the foundation.