The Barbarastollen underground archive is an underground archive intended to preserve Germany’s cultural heritage from man-made or natural disaster. The Barbarastollen is located in a disused mine near Freiburg im Breisgau, Baden-Württemberg, Germany. It holds microfilms with about 900 million images from German archives and museums.

More information on the English Wikipedia page [1] - and considerably more on the German Wikipedia page [2].

The website, in German, is [3]