The Crypt is the only piece remained of the Hl. Barbara Church that once stood on the location of the present-day main square of the town. It was built mainly with the money donated by miners, who wanted their patron saint to be watching over their safety in the pit and above the ground.
During the allies' bombings the church was severely damaged and then pulled down completely in 1951. The crypt was reopened to the public in 2007 after total reconstruction of the square according to the plans of the architect Boris Podrecca.
On 22 June, the name day of the Hl. Acacius, there is a church service in the crypt. In front of the crypt itself there is a gallery.
The gallery and the crypt are located under the main square Mestni trg in Idrija.