Counter-mine labyrinth

Counter-mine passages were intended to detect and destroy enemy tunnels. The garrison could mount an underground defence before hostile mining threatened the fortifications above. The full network beneath the defensive slope extends for around seven kilometres. This is the size of the defensive system, not the length of the visitor route.

Passages range from 90 to 180 centimetres in height and from 60 to 120 centimetres in width. Visitors walk in single file and must bend down in the lower sections. The floor can be uneven, with puddles in places. Temperatures remain at 8-10 degrees Celsius throughout the year, so clothing and footwear suitable for cool underground conditions are needed. The labyrinth can only be visited with a guide, and the tour lasts about an hour and a half. Children may enter from their fifth birthday. The tour explains the purpose of the passages and the construction of mine chambers.