Who is not interested in unsolved mysteries? Let's not forget about the five mysteries that are still unsolved. 1. Erdstal Very narrow underground tunnels have been found all over Europe, named Erdstall. More than 700 such tunnels are found in Bavaria, Germany alone. The tunnels are very narrow; About one and a half meters high and one meter wide. Interestingly, it is not yet known who built this tunnel, or when it was built, or for what purpose. Some scholars believe that these may have been created for religious or spiritual purposes. Some, however, say that the tunnels may have been ready to be used as shelters. But to date no written map or evidence of construction of these tunnels has been found. Why the tunnels were built with such secrecy is a mystery.Read the book for many others...