St. Hyacinth chapel was built in 1304 as a part of the Dominican monastery (a chapterhouse connected to a cloister) After its dissolution by decree of Emperor Joseph II in 1782, the chapel changed owners a few times and fell into disrepair. Its destruction was complete after the 1863 fire. Through the efforts of a priest, the chapel was bought from its Jewish owners at that time and renovated. During the renovation in 1894, the chapel was covered with a gable room closed with gables with recesses. The chapel was consecrated in 1894 and has remained in the hands of Salesians since 1898. It retained its initial Gothic style: it is a brick chapel on a rectangular plan with a 2-bay body with a gable roof and a bell turret covered with a cupola. A stone portal adorns the entrance. Outside, in the location of the walls connecting the chapel to the monastery, the chapel is framed by brick buttresses (early 20^th century). Stained glass windows have the shape of elongated rectangles topped with arches. Above the entrance, there is a neo-Renaissance wooden choir with a piano, situated on stone supports and accessed via a stone staircase with a metal balustrade. On the southern wall, there is a marble early Baroque epitaph to Mikołaj Mstowski (1656) and the crypt of Oświęcim dukes is under the floor.