St. Mary's Cathedral (Katedra Niepokalanego Poczecia N.M.P) is a gothic church erected between 1300-1333. Initially serving as a Catholic church, the building was from the 16th century till the end of World War II a temple for the Protestant faith. Since 1945 it again is a Catholic house of worship.
http://www.visitpomerania.eu/cities/koszalin/attractions/saint-marys-cathedral/