Some of you may have heard of the massive Richard Mine complex in the former nation of Czechoslovakia during WW2. Much of the mine was a factory for the Panther tank.

A large portion of the mine however (about a third) was used for some other purpose. At the end of the war it was deliberately collapsed by high explosives to seal it off.

Since the mine was relatively unknown to Westerners do any members of this forum know or have some idea what was sealed in the remaining mine ?