Built in the 16th century, St. Mary’s Chapel was designed and constructed under the direction of master builders Bernt Wolt and Gert Koningk, who were invited from Münster. Like the church choir, the chapel features stellar (star-shaped) vaulting and a polygonal apse. Nowhere else in Estonia is there another Late Gothic building of such richness in form and decoration.
The interior acquired its present appearance during the 19th century, when it was restored in a style inspired by authentic Gothic architecture. The altarpiece, The Transfiguration of Jesus (1833), was painted by the Tallinn artist Carl Siegismund Walther (1783–1866).
A masterpiece of woodcarving is the portal (1839). The composition on the inner side of the door depicts the peaceful Kingdom of Christ, as prophesied by Isaiah in Isaiah 11:6–9.
