Kruszwica is a town in central Poland, in the Inowrocław County in the Kuyavian-Pomeranian Voivodeship. It has a population of 9,161. Initi…Kruszwica is a town in central Poland, in the Inowrocław County in the Kuyavian-Pomeranian Voivodeship. It has a population of 9,161. Initially founded in the 6th century, Kruszwica is the oldest town in the region and features a medieval castle with a 12th-century Romanesque church. It is situated on the shores of Gopło Lake in the historic region of Kuyavia.