Whoever complains about our 9-5 job, should visit these caves to realize the definition of hard work. At a freezing cold temperature combined with a nasty 98% humidity, the people of Maastricht have sawn-off more than 200 kilometers long underground marl-stones to build this defense system.

A short history behind the caves:
These mountains of Marlstones (sort of/like limestones) were formed from the accumulation of bones and shells of animals deposited at the bottom of the then sea. (It’s not hard to believe that this portion of Netherlands was a sea once, Isn’t it?).

Romans, during their era in the Netherlands (50 years Before Christ) materialized the limestones as a building / construction substance. Though limestones are very soft in nature, they get extra-strong when let them dry or heat. That was the start of these caves!

They took away tons and tons of limestones from these mountains for construction of houses, churches, safety walls and towers. We can still see many houses in the Vrijthof Square (the center of Maastricht) constructed with limestones. Continuous evacuation of stones started making caves / tunnels underground.

Then, in the late 17th century when this region has become a favorite of all the invaders, people of Maastricht started used these caves as their temporary hiding station. With a fertile delta created by river “Mass”, this region was always on demand; Maastricht city was invaded 21-times by different empires and dynasties; and every time these caves provided safe shelters to the local people.

People extended the tunnels to move from Netherlands to the Belgium region underground, and vice-versa. We can still see some writings and paintings from the 17th century inside the walls of the caves. They made not only mandates like toilets and cooking ovens inside, but also built a deep well for water inside the caves.

These tunnels were extended to about 14-kilometer-long during the 18th century, so that I could house up to 25,000 refugees. The caves underneath the Saint Pietersburg Mountain made a critical contribution during the World War-II. It’s known that as much as 45,000 people were living inside these tunnels for about 10 days.

Then there came ENCI (Eerste Nederlandse Cement Industrie) translated as the “First Dutch Cement Industry) who made good use of these limestone caves and extended them to a maze of 20,000 tunnels and to a distance of 230-kilometer long.

Back To the Present 😃:
In the early year-2000 period, ENCI stopped excavating further, since all the usable stone layers were run out. But already a large portion of the corridors got demolished because of the dynamites used during stone excavation. We see only about 80 kilometers long corridors are existing today. Around 2006 period, the Dutch national art treasures took over these caves and started allowing tours inside these caves.