Efringen-Kirchen is a municipality in the district of Lörrach in Baden-Württemberg, Germany.

In 1936 plans were drawn up to turn the location into the "Gibraltar of the West" with two kilometres of underground passages linking gun emplacements and bunkers.

The site was to host an underground garage for over 100 tanks, 3600 men and as part of the Siegfried Line it would dwarf similar Maginot Line fortifications.

Work began in 1937 and Hermann Göring visited in the spring of 1938.

By 1939 several installations were complete but as the war progressed advantageously for the Germans in 1940 the site remained unfinished.