Part Baroque palace, part Renaissance fortress, Poland’s third largest castle looks like something lifted from a fairytale.
But beneath the lavish architecture lies a darker story. Here, deep in Poland’s Owl Mountains, lies a vast underground Nazi complex tied to one of the Third Reich’s most mysterious construction projects and, legend has it, a lost train filled with stolen gold.
Książ’s history stretches back to the Middle Ages, when Silesian duke Bolko I the Strict built a fortress on this hilltop. Over time it expanded into a grander residence.
In 1466, Hans von Schellendorf acquired the castle and named it Schloss Fürstenstein — a title it would keep until the end of World War II. As Lower Silesia was a part of Prussia until the 20th century, the castle became one of Germany’s most significant aristocratic residences.
That legacy is still visible today. Visitors enter through manicured gardens before stepping through huge front doors into ornate rooms that wouldn’t be out of place in the palaces of Vienna or Paris.
A darker chapter
Maximilian Hall — filled with grand chandeliers, marble fireplaces and walls of rich stucco — reflects the castle’s heyday, when it was frequented by royalty from across Europe. Another highlight are rooms that belonged to British-born Princess Daisy, wife of Hans Heinrich XV von Hochberg, the castle’s last owner. These are decorated in playful pink, with large mirrors and a plush sofa.
A tour of the castle passes through many more decorously appointed rooms, lined by oil paintings and antique furniture. But then, the scene suddenly shifts.
Tucked away in what initially appears like just another regal chamber, are two dreary-looking elevator shafts — an abrupt contrast to the ornate surroundings
“These lifts were built by the Nazis in 1944,” says Mateusz Mykytyszyn, Książ’s head of public relations. “The shaft goes 50 meters below the castle, to the bunkers and serves as a quick evacuation route.”
The transition from lavish salons to utilitarian machinery is jarring. It marks the beginning of a darker chapter — one tied to Project Riese, one of the Third Reich’s most secretive construction efforts.
In 1944, with World War II raging, the Nazis seized control of the castle from Count Hans Heinrich XVII, who had already relocated to England. Książ and the Owl Mountains then became a hub for Project Riese — German for “Giant.”
The project aimed to create a network of massive underground facilities across Lower Silesia. Seven major subterranean complexes have been discovered so far, but the true purpose of the tunnels remains uncertain. Many documents were destroyed or hidden by the Nazis as the war ended.
Brutal conditions
The tunnels at Książ lie away from the heart of most of the Project Riese structures, deepening the mystery here. According to Mykytyszyn, it’s widely assumed this is because the castle was intended to become Adolf Hitler’s Headquarters — though definitive proof has never emerged.
What is known is the human cost.
More than 13,000 prisoners were brought to the region to excavate tunnels and construct underground infrastructure. Organisation Todt, Nazi Germany’s civil and military engineering body, oversaw the work, relying heavily on inmates transferred from Auschwitz and Gross-Rosen concentration camps — many of them Jewish prisoners.
Workers faced brutal conditions and relentless pressure. Disease outbreaks, including typhus, were common. Researchers estimate that around 5,000 people died during construction.
Today, that history is a central part of the visitor experience — especially underground.
The tunnels beneath Książ stretch nearly a mile. Some passages are constructed from reinforced concrete, made smooth and precise. Measuring five meters high, or roughly 16.5 feet, they’re wide enough to drive a car down.
Some sections are just bare rock. In one tunnel, the remains of a narrow-gauge railway used during excavation can be seen.
There are modern exhibitions here that use projections and audio to tell the story of Project Riese. Screens illuminate dark chambers with archival images and historical context. The effect is immersive and — particularly because of the human cost of creating the space they’re in — often unsettling.
Many visitors say it’s the scale that leaves the deepest impression.
Buried gold?
Despite the documented history, myths continue to swirl around Lower Silesia — especially the story of a hidden train loaded with stolen Nazi gold.
“Even today, many people are looking for the treasures and hidden tunnels here,” says Michał Miszczuk, a local guide at Underground City Osówka, another major Project Riese complex nearby.
The legend suggests that during their retreat from Wrocław — then Breslau — in 1945, Nazi forces concealed a train filled with valuables somewhere in the Owl Mountains. In 2015, treasure hunters received permission to excavate a suspected site near Wałbrzych known as Zone 65, but found nothing.
But the mystery persists, fueled by missing documents and the many undiscovered tunnels believed to remain sealed. When the Nazis retreated as the Red Army approached in 1945, they destroyed or hid entrances to many underground passageways.
“Lower Silesia has been German for centuries,” explains Miszczuk. “Even if they knew the war was lost, they were sure that they would get this land back.”
Believing in a buried treasure is easier when standing in the dark tunnels of Osówka, which are rough and rocky, in contrast to the mostly smooth concrete of Książ.
The complex spans roughly two kilometers, or just over a mile, with towering chambers and a 48-meter vertical shaft. Some researchers speculate that it may have been intended as a central hub connected to other Riese sites.
Here, visitors walk through dim corridors that end abruptly in rubble. A subterranean stream even allows for small boat tours through pitch-black sections of the tunnels.
Abandoned equipment remains scattered throughout the complex, underscoring the harsh conditions endured by workers. Exhibitions here focus heavily on the human toll — an intentional effort to ensure the site serves as a place of remembrance as well as tourism.
Today, Książ Castle is one of Poland’s most popular attractions. Spring brings crowds for the Festival of Flowers and Art, while nearby hotels housed in former outbuildings accommodate visitors year-round. The castle also hosts conferences, weddings and cultural events.
The global fascination with the supposed Nazi gold train has boosted international attention. Yet the site’s managers face a delicate balance in promoting tourism while honoring the suffering tied to its history.
For many travelers, that contrast defines the visit.
After hours spent underground, stepping back into daylight feels like a release. The rumors of buried treasure may draw people in, but the deeper story is one of ambition, secrecy and immense human tragedy.
