Vistula Mouth Fortress

Wisłoujście Fortress is a historic fortress located in Gdańsk by the Martwa Wisła river, by an old estuary of the river Vistula, flowing into the Bay of Gdańsk. The fortress is located close to the Wisłoujście borough, Westerplatte and the Port Północny. It is listed as a Historic Monument of Poland.

Source: Wikipedia