I know of one huge black snake that is or was under the Vatican. I think it's still there somewhere, because as far as I know, the Vatican was hermetically sealed "for unknown" reasons. No one can go in and no one can go out.

There is also something under Prague in the old town. They fed it from the basement of the HardRock https://www.hardrockcafe.c... . The entrance to that room was barred and separated by a sliding white wall. So whoever doesn't know about it won't get there. I didn't tell anyone because no one would have believed me anyway. I got there by accident and what I saw there, the horror....we know, but most people would rather die than admit the truth that we are not alone...