The oldest church of Northeim is Saint Fabian's and Sebastian's Chapel which was built in a typical gothic style in the middle of the 14th century and renovated in 1985/86. Saint Sixti's Church was built from 1464 to 1517. It houses a gothic altar dating from 1420 and another altar created in the 16th century. After the church had been allocated to the Protestants in 1539 there were no Catholics living in Northeim for several decades. The first catholic church to be built after the reformation was Saint Mary's Church outside the historic town centre which was founded at the end of the 19th century.