The tree-nave basilica built in the Romatic style initially lacked the west tower so typical today. Instead, the building had two flanking towers to the side of the Romanesque chancel. It was not until a rebuilding phase in the 12th century that the church received the tower, which gave the building a new demarcation to the west. After the destruction of the choirduring an uprising of the Siegburg citizens, the area was rebuilt from 1403 onwards, this time in Gothic style.
In 1649, the church was destroyed by fire, and a baroque building in the style of the time was erected on its ruins. The building was characterised by a mighty crossing of the same height as the nave. This was given a uniform level by flattening the pointed arches of the Gothic choir. The large windows in the north and south walls of the crossing gave the building a light and soaring airness. However, the ornamentation on the columns and pillars was quite sparse and could not be compared with the ostentatious Baroque decoration in southern Germany.