St. Anne's Church in Warsaw is a significant architectural landmark that showcases the city's development since 1454, even before Warsaw became the capital of Poland. The church, which has undergone multiple reconstructions, features a blend of various architectural styles. Unfortunately, during the construction of an expressway in 1949, the church suffered damage due to the failure to secure the slopes of deep excavation, resulting in cracks in the walls and vault and the northeastern part of the church subsiding. Despite the implementation of protective measures, the structure has sustained new damage in recent years. This article presents a case study on assessing cracks in masonry vaults using numerical analysis and proposes a method for strengthening the structure.