This original Gothic church was founded for the Order of Augustinian Hermits by Wenceslas II. in 1285 and completed in 1379, along with an Augustinian Monastery and St Thomas' Brewery. In the richly decorated interior there are paintings and statues by Czech artists including Karel Škréta and Václav Vavřinec Reiner.
It was beautifully rebuilt in the Baroque style. The high altar is decorated with two Rubens paintings, the originals have been replaced by copies and are deposited at the National Gallery.