This pedestrian tunnel in the city of Zagreb runs underneath the historic neighborhood of Grič. Built during World War II, the tunnel was originally intended to serve as a bomb shelter and transport link through the hill of Gornji Grad. It measures 350 meters long and up to 5.5 meters wide, connecting Mesnička and Stjepan Radić Streets. Construction began in 1943 and finished 1944. The tunnel was harshly criticized for its expense, and many argued that it was not necessary. Work continued nevertheless, though changes were made to the project. The original plans included a large underground hall to be placed in the center. But in the end, that feature went unrealized, and only an east-west transport corridor was finished.

After the end of World War II, the tunnel was remodeled and the planned central hall was added. It was used as a warehouse for a food company but was soon forgotten and largely abandoned. It attracted unhoused people and others seeking temporary shelter.

Interest in reviving the tunnel started in the 1990s, when energetic rave parties were held inside. Proposals for the remodeled tunnel included a "museum of senses" and a lift that would allow people to reach the neighborhood above without climbing the steep hill. 

But instead in 2016, the remodeled tunnel opened to the public as a cultural center. You can literally walk through the history of Croatia and Zagreb and familiarize yourself with different historical events through information displays and objects. The tunnel is structured into separate compartments that are arranged for various displays about culture, everyday life, and science. Curators have used different image and light effects and interesting sound options.

The central underground hall has been turned into a Rain Room where visitors walk under water drops (the Tunnel provides umbrellas) and images of famous persons from Croatia are displayed. Another fascinating exhibit is a Tesla machine that uses sound and electricity and fires out a lightning effect analogous to a Tesla coil.

Update as of June 2023: The tunnel is now devoid of many artifacts.