The Klodzko hill has played an important strategic role for centuries, straddling the traditional borderland first between the Polish and Bohemian kingdoms, and then later Prussia and Austria. There's been a fortress of one kind or another here for around 1,000 years. The present massive structure dates from the middle of the 18th century, when the Prussians defeated the Austrians and embarked on a massive rebuilding project using prisoners of war as laborers. Early on, Napoleon shattered the fortress's illusion of invincibility by capturing it in 1807. During World War II, the Nazis used the fortress to hold political prisoners. Today, it is the region's leading tourist attraction, both for its tower with commanding views over Klodzko's hinterland and its labyrinth of underground tunnels once used for troop mustering, hiding, and escape, if necessary. The tunnels can be seen by guided tour only. Be sure to bring a jacket, even in summer, as it can get quite cold down there. To find the entrance to the fortress, head to the top of the main square and walk left on Czeska Street.