The Skrilje Bunker, located 90m below the ground in a forest at a sealed-off military base near the town of Kocevje, Slovenia, was recently opened to the public.
The 800 sq m labyrinth was built in the 1950s for former Yugoslav elite.
Almost three decades after the end of the Cold War, secrets from an era of espionage are resurfacing in Slovenia.
In Postojna, a town about 1½ hours from Kocevje, a secret room with surveillance technology in a hotel was discovered recently.
Hotel Jama, where the late Yugoslav leader Josip Broz Tito used to regularly stay and host guests, is located next to Slovenia's famous Postojna cave.
The secret room was found to lead directly into the interior of the cave, according to Voice of America.