The Celtic fortification system on the Houbirg once spanned approximately 60 hectares.
The 'Hohler Fels' is not purely natural; it was partially expanded by historical mining activities.
During World War II, the site was the location of a top-secret underground factory project known as 'Doggerwerk'.
The Doggerwerk tunnels were built by prisoners from the Flossenbürg concentration camp under extreme conditions.
The cave entrance acts as a natural cold trap, often holding snow or ice late into the spring.
The plateau is protected as a cultural monument due to its Iron Age archaeological significance.
The Houbirg, also known as the Hohler Fels, is a prominent plateau and rock formation overlooking the Happurger Stausee in the Nuremberg region. The site features a cavernous rock formation created by natural geological processes and human excavation. It sits within the perimeter of a massive prehistoric Celtic hillfort dating back to the La Tène period. The area serves as a significant archaeological zone with visible remnants of ancient dry-stone walls. Hikers access the site via steep trails ascending from the Happurg reservoir. The summit offers panoramic views of the Pegnitz valley. The geological composition consists primarily of Jurassic limestone, characteristic of the Franconian Alb.
The ledge directly above the Hohler Fels looking down towards the reservoir.
Wear sturdy, non-slip hiking boots, as the trails are steep and the ground near the cave can be slippery.
Bring a flashlight if you intend to look closely at the cave entrance or tunnel structures.
Combine the hike with a circuit around the Happurger Stausee for a full-day excursion.
Do not attempt to enter the fenced-off or blocked sections of the historical tunnels, which are structurally unstable.
Stay on marked trails to protect the fragile archaeological site and do not disturb cave-dwelling bats.
