The Berlin Underworlds Association (Berliner Unterwelten) offers a unique experience beneath the surface of Berlin, guiding visitors through historical bunkers, tunnels, and other subterranean structures. Founded in 1997, this non-profit organization aims to document, preserve, and provide access to Berlin’s extensive underground facilities. Since 1999, the association has been organizing guided tours that reveal the hidden history of the city, including WWII bunkers, escape tunnels, and even old brewery cellars.

One of the highlights is the tour through the bunkers beneath Gesundbrunnen Station, where visitors can explore the structures used during the Second World War as civilian air raid shelters. These underground tours offer a vivid insight into the challenges faced by Berlin's residents during the air raids. There is also a focus on the East Berlin escape tunnels that allowed people to flee to the West during the Cold War, with guides providing moving stories of the individuals who attempted these daring escapes. In addition to these tours, the site also features the Fichtebunker, a structure that has served multiple purposes over its 130-year history, from a gasometer to a mother and child bunker during the Nazi era.

The association offers various themed tours, such as Dark Worlds, which focuses on WWII bunkers, and tours that explore East Germany escape tunnels and hidden historical artifacts. Visitors can also attend exhibitions, including the Myth of Germania exhibition, which details the Nazis' grand architectural plans for Berlin. Tours are available in multiple languages, and the association hosts seminars and educational programs throughout the year. Tours typically last around 90 minutes, and due to the underground nature of the tours, participants are encouraged to wear warm clothes and sturdy shoes.