Travelers to Maastricht, located in the southern Netherlands, often admire its cobbled streets and historic architecture, but the city's most notable features may lie underground. The area is home to approximately 500 quarries, remnants of mining activities dating back to Roman times, with the limestone quarries in continuous use since around 1300.
Although limestone quarries were abandoned in the 1920s, these underground sites have since been repurposed. During World War II, they served as shelters for the local populace and valuable art from Dutch museums. Jos Notermans from the Menno van Coehoorn Foundation notes that while the structures share an underground nature, each has its unique history and characteristics.
Interest in the subterranean features of Maastricht is evident, as historical records from the 17th century indicate guided tours of the quarries. Currently, most caves are off-limits to the public, with penalties for trespassers, though tours are available through Maastricht Underground, revealing the city’s hidden history.
The Fort Sint Pieter, constructed in the early 18th century, is notable for its network of tunnels, once the largest subterranean complex until the 20th century. The fort features whitewashed gallery walls and a well-designed defense system, which includes embrasures for musketeers and cannons capable of hitting targets at significant distances.
Within the St. Pietersberg hill, approximately half of the original tunnels remain, featuring graffiti and drawings from various eras, including a significant depiction of a mosasaur. During World War II, around 800 artworks were safeguarded in these caves, with famous pieces like Rembrandt's "The Night Watch" stored in a concrete vault known as the Kluis.
The Zonneberg Caves, part of the same quarry system, feature more linear tunnels and were prepared for mass evacuations during the war, equipped with essential facilities for the city's population.
Another significant underground structure is the Waldeck Casemates, a defensive system built in the late 16th century. These tunnels housed soldiers who monitored for enemy movements and were converted into air raid shelters during World War II.
Additionally, the former NATO control center under Cannerberg served as a strategic military site during the Cold War, coordinating operations for West German air defense. Although officially secret, its existence was generally known, particularly during heightened tensions like the Cuban Missile Crisis.
Although much of the original infrastructure has been removed, remnants of the NATO complex, including control rooms and social areas, remain accessible for tours. Interest in these sites has surged since Russia's invasion of Ukraine, prompting discussions about their potential use in contemporary conflicts.
Notermans emphasizes the value of Maastricht's underground structures, likening them to the Metro system in Kyiv, which currently serves as a refuge against threats.