Three architectural styles are represented on the church tower: a Gothic storey was added to the two lower Romanesque storeys at the end of the 14th century and the Baroque (Welsch) dome was added in 1709. When an air mine fell between St. Petri and St. Patrokli in 1945, the Gothic choir was almost completely destroyed. Its reconstruction according to the old model until 1955 was practically equivalent to a new building. The areas around the church were cemeteries until the 19th century.
A large part of the original ornamental painting of the church, which is the oldest and one of the best-preserved examples of a very widespread decorative system in Westfalen, was uncovered around 30 years ago. The crucifixion group on a pillar of the north wall, created around 1400, is attributed to the painter Conrad von Soest or his school. Other items worth seeing include a winged altar from Brabant (around 1525), a late Gothic baptismal font (late 15th century) and a pulpit with rich figural carvings (1693).