Frombork [ˈfrɔmbɔrk] (German: About this sound Frauenburg ) is a town in northern Poland, on the Vistula Lagoon, in Braniewo County, Warmian-Masurian Voivodeship. It had a population of 2,528 as of 2005.The town was first mentioned in the 13th century. In the early 16th century it was the residence of the astronomer Nicolaus Copernicus, who used it as a site for several of his observations. The town and its 700-year-old cathedral were badly damaged in World War II.