The Hel Fortified Area (Polish: Rejon Umocniony Hel) was a set of Polish fortifications, constructed on the Hel Peninsula in northern Poland, in close proximity to the interwar border of Poland and the Third Reich. It was created in 1936, upon a decree of President Ignacy Moscicki. It covered most part of the peninsula, and during Polish September Campaign, it was the last place of Poland to surrender to the invading Wehrmacht (for more information, see Battle of Hel). During World War II, the naval base in Hel was used as a major training facility for U-boat crews.