The Church of St Catherine of Alexandria is Brodnica's main parish church and the finest piece of brick Gothic in town. Construction began in the early fourteenth century, under Teutonic patronage, and the building has the strict rectangular nave-and-aisles plan typical of the order's foundations along the Drwęca and Vistula.
The interior is comparatively modest after centuries of fire and remodelling, but a few medieval pieces survive — Gothic frescoes in the choir, a Renaissance epitaph or two, and a heavy 17th-century main altar. The slender brick tower is visible from the castle ruins and is one of the landmarks of the old town.