The Secret Underworld: Uncovering Poland’s ‘Project Riese’

The Secret Underworld: Uncovering Poland's 'Project Riese'

When most people plan a weekend trip to explore Polish history, they usually think of walking through quiet museum halls or looking at old paintings in a castle.

But if you head to the beautiful, forested Owl Mountains (Góry Sowie) in Lower Silesia, history isn't just something you look at behind glass. It is a massive, terrifying labyrinth of pitch-black tunnels hidden hundreds of meters underground.

Welcome to the dark, unsolved mystery of Project Riese (The Giant).

The Subterranean City

During World War II, as the bombing of German cities intensified, the Nazis decided they needed to move their most important military production underground. In 1943, they began carving a colossal, interconnected subterranean city deep into the rock of the Polish Owl Mountains and beneath the nearby Książ Castle.

Tens of thousands of prisoners were forced to dig out massive concrete halls, railway stations, and deep shafts. But in 1945, as the Soviet army approached, the project was suddenly abandoned. The retreating soldiers blew up the entrances and flooded the lower levels, taking the blueprints with them.

To this day, nobody actually knows what Project Riese was truly meant for. Was it an underground headquarters for Hitler? A secret factory for experimental weapons? Or a nuclear research facility? The true purpose remains one of history's greatest mysteries.

An Adrenaline-Pumping Weekend Adventure

For expats and migrants looking for an epic travel experience, exploring this region is an absolute must. It offers a weekend adventure that is completely different from a standard city break.

Today, several parts of this massive underground complex have been discovered and safely opened to the public. You actually put on a heavy plastic hard hat, step into the freezing, damp air, and follow a guide deep into the earth. You will walk through massive, echoing concrete caverns, and in some complexes, you even get to board a small metal boat and float through the flooded, pitch-black tunnels.

It is an incredibly atmospheric, slightly chilling experience that taps into a dark and fascinating chapter of local history. It is the closest you will ever get to feeling like an explorer uncovering a hidden world.

How to Prepare

Because the tunnels are carved directly into the mountain, the temperature inside stays around a freezing 7°C to 8°C all year round—even if it is 30°C outside in the middle of summer! Always bring a thick jacket, wear sturdy hiking boots (the floors are often wet and muddy), and be prepared for a real adventure.

Useful Resources

• Kompleks Osówka (Osówka Complex) – One of the most advanced and fascinating parts of Project Riese. Their English website allows you to book the "Extreme Route," where you navigate flooded tunnels on wooden planks.

• Sztolnie Walimskie (Rzeczka Complex) – Another fantastic, highly atmospheric section of the underground city. They offer excellent historical tours detailing the tragic human cost of the construction.

• Zamek Książ (Książ Castle Underground) – The Nazis also dug massive tunnels directly beneath this beautiful, fairy-tale castle. You can take a guided tour of the depths before exploring the lavish palace above.

• Lower Silesia Official Tourism Portal – Since all these complexes are located in Dolny Śląsk (Lower Silesia), use this portal to plan the rest of your trip, find a cozy mountain guesthouse, and figure out the regional trains.

• YouTube: Exploring Poland's Terrifying Underground Fortress – Check out this great video to get a first-hand look at the chilling maze of narrow passageways hidden beneath the Kłodzko Fortress, another incredible piece of subterranean history in the same region!

Vocabulary Cheat Sheet