On the eastern side of Március 15 tér, a Romanesque church was first built in the 12th century within a Roman fortress. You can still see bits and pieces of the fort, Contra Aquincum , protected under Plexiglas on the square. The present church was rebuilt in the 14th century and again in the 18th century, and you can easily spot Gothic, Renaissance, baroque and even Turkish – eg the mihrab (prayer niche) in the eastern wall – elements.
The best times to visit the church (if you want to avoid services) are between 10am and 3pm and 3pm and 5.30pm Wednesday to Saturday.