Hans Hagen of the Vsetin underground

I was wondering if I should reveal the exact location of this interesting monument. In the end, I won't. I'm not entirely sure her visit is entirely legal. Even though - most Vsetinians know about it anyway, a friend admitted that they used to go there to play as children. and recently a geocaching treasure has also appeared there. So what.
An underground tunnel about 200 meters long. Encased in stone. In the 19th century, streams were not yet closed...