The chapel of St. Martin was built around the 2nd quarter of the 14th century. The first time was mentioned in 1421. At that time, it was surrounded by a cemetery on which the poorer residents of the city were buried. It was intended for the Polish-speaking pastoral care, and then in the 17th and 18th centuries to serve the pastoral care of the Catholic German-speaking population living in the parish. Since the 19th century, the chapel has lost its sacred function.
It is a small temple with dimensions of 13,5 x 9,6 meters, aisleless, orientated, made of brick with flemish bond. The front elevation has a pointed portal and two circular blendes, topped with a band frieze in the upper zone. The top is triangular with seven angularly arranged lesenes that pass into pyramidal pinnacles with reconstructed crockets. Between the lesenes there are pointed blendes, two of which have an attic windows at the bottom. The eastern façade originally had a large pointed window, reduced and walled in the 17th century. The eastern top is decorated with pinnacles and two pointed blendes. The interior of the chapel is covered with a flat ceiling.
Webpage odznaka.kuj-pom.bydgoszcz.pttk.pl, Kaplica św. Marcina w Chełmnie.