At the beginning of the 1950s during the Cold War, four tunnels were excavated under the Babická plateau in the Křtinské údolí on the left (southern) slope in the area between Švýcárná and the Vaječník groove. Their purpose was to be used for war production in the event of a conflict. It is likely to be linked to arms production in the nearby Adamovské strojírny. After the emigration of the chief engineer and the disclosure of the plans in the Swiss press, it was decided to end the digging of tunnels and to wall up the buildings. Since then, the abandoned tunnels have been crawled by dozens of curious cavers and tourists. In recent years, an expert geological survey was carried out in the tunnels. The tunnels were excavated on the slopes of the Jelenec hill: tunnels I and II on the east and tunnels III and IV on the north. slope. The underground spaces of the tunnels near the entrances are inhabited by a community of invertebrates that are partly adapted to life in the dark and damp. Around tunnels III and IV. Josefovská údolí educational trail leads.
Tunnel No. I is located near the Kostelík cave. It is approx. 150 m long and slopes slightly towards the SW. Just before the end of the tunnel, there is a cave-in behind which approximately half of the tunnel is permanently flooded. Also before the cave-in there is water from about halfway up to waist height. Only exceptionally is the bottom dry and it is possible to collapse.