The Collegiate Church of St. Gall and Otmar was designed by Peter Thumb and built between 1755 and 1767. It has been the cathedral of the Diocese of St. Gallen since 1847.
The twin-tower facade was completed in 1761 under the direction of Johann Michael Beer.
The rotunda inside the Collegiate Church of St. Gall and Otmar has a diameter of 37m. Overall the ceiling paintings in the St. Gallen Cathedral cover a surface area of 2500 square meters. They were painted mostly by Josef Wannenmacher. The painting inside the rotunda shows paradise with the Holy Trinity in the centre surrounded by saints.