Berlin Underworlds have been organising tours of Berlin's underground secrets for 20 years. To celebrate, they are - for one night only - opening up all of the sights usually only accessible on one of their tours. These include: the operation bunker at Teichstrasse, the bunker at Pankstrasse, the Blochplatz bunker, the Myth of Germania exhibition, the bunker at Gesundbrunnen, the AEG-Tunnel, the brewery cellars near Bernauer Strasse and the Fichtebunker in Kreuzberg. The tour starts at Paracelsus-Bad U-Bahn station. Places are limited so buy tickets in advance.