Włocławek (vlôtsläˈvĕk) [key], Rus. Vlotslavsk, city (1994 est. pop. 123,000), Kujawsko-Pomorskie prov., central Poland, a port on the Vistula (Wisła) River. It is an agricultural market center and has industries producing cellulose, paper, chemicals, and food products. Nearby are salt domes, lignite deposits, and sulfur springs. The city was founded in the 12th cent., passed to Russia in 1815, and reverted to Poland after World War I. Landmarks include a 14th-century Gothic cathedral and a 17th-century episcopal palace.