Bydgoszcz (390,000 inhabitants) near the Vistula is the biggest city of the region and an important trade centre. The old buildings on the bank of the river Brda are worth a closer look. In ul. Grodzka there is a couple of splendid old granaries today housing a museum and a gallery. In the city centre there are numerous examples of Art Nouveau architecture. Biskupin, situated between Bydgoszcz and Gniezno, has an archaeological open-air museum, where a Lusatian fortified town from the 4th century B.C. has been reconstructed. It consists of a hundred wooden houses surrounded by a dyke.