The walls of the church are high , supported by buttresses ; these were probably added because of fears that earthquakes might otherwise damage the building . The towers are not part of the original construction but were added later ; the north tower was damaged in the 1985 Mexico City earthquake . Despite large windows , the interior of the church is dark and the only architecturally significant piece besides the ceiling is a stone door with the shield of the Dominicans that leads to the abbey . There was doubtlessly a wooden altarpiece originally , but that has disappeared . The only paintings are of the Virgin of Guadalupe and an 18th century anonymous painting of Calvary
1985 Mexico City earthquake
1985 Mexico City earthquake
Tepoztlán