Westerplatte is a long peninsula at the entrance to the harbour. When Gdańsk became a free city after WWI, Poland was permitted to maintain a post at this location, at the tip of the port zone. It served both trading and military purposes and had a garrison to protect it. WWII broke out here at dawn on 1 September 1939, when the German battleship Schleswig-Holstein began shelling the Polish guard post. The garrison, which numbered just 182 men, held out for seven days before surrendering.

The site is now a memorial, with some of the ruins left as they were after the bombardment, plus a massive monument put up in memory of the defenders.