St. Mary's Church (Stadtkirche St. Marien) is one of the most important late-Gothic hall churches in Saxony. Construction began in the 14th century and continued into the early 16th century; the twin towers that define the Pirna skyline were added in stages and give the building its distinctive profile above the market square. The interior is a single large hall with slender columns and ribbed vaulting — a type of construction popular in Saxony that creates a sense of spacious unity rather than the high-nave drama of French Gothic.
The church's two main treasures are both in the nave. The Tulip Pulpit, carved in 1545, is a late-Gothic masterpiece that somehow survived both the Reformation iconoclasm and the 20th century intact. The astronomical clock on the north wall dates from the late 16th century and still displays the positions of the sun and moon. Bellotto painted the church interior as well as the exterior, and his 18th-century paintings provide a detailed record of what the space looked like before later modifications. Entry is free or by donation.