The locals call them caves, but they are mostly mines. For centuries the people of Valkenburg quarried marl, the soft chalk-like limestone that gives the region its pale buildings, and what they left behind is an underground labyrinth tunneled directly under the town. Some passages are now display halls of charcoal drawings and marl sculptures, accumulated by generations of bored quarrymen and modern artists who liked the medium. One former quarry has been recreated as the catacombs of Rome by the architect Pierre Cuypers, who lived in Valkenburg in the early twentieth century and seems to have decided the town needed its own Italy. Another is dressed as a coal mine. Every December, the largest caves fill with Christmas markets, the temperature underground holding steady around twelve degrees while wet weather rages above. Few towns of nine thousand people have so much of themselves underneath themselves.

Pierre Cuypers was the architect who designed Amsterdam's Rijksmuseum and Centraal Station, but he spent several years in Valkenburg in the early twentieth century, and the town accumulated his attentions like a hostess accumulates flowers. A Gothic Revival chapel on the Cauberg, the steep hill outside the center. Several tombs in the graveyard. A restored medieval church. A hotel he designed himself. An open-air theater. The replica Roman catacombs in the quarry. Cuypers helped turn Valkenburg from a place that had occasionally been a holiday destination since the railway from Maastricht arrived in 1853, when Valkenburg got the station that is still the oldest surviving railway station in the Netherlands, into a place that was committed to the business of being visited. The town now hosts more than a million overnight stays a year and is openly trying to climb back from the mass-tourism years of the 1960s through the 1980s toward something it calls quality tourism.

Valkenburg was occupied by Nazi Germany for four years, four months, and one week. On 17 September 1944, the American 30th Infantry Division liberated the town. The townspeople greeted the soldiers with tulips and bread. That is the entire surviving image: not a battle, not a procession, just tulips and bread. The 30th Infantry, nicknamed the Old Hickory Division, would go on to fight through the Hurtgen Forest and the Bulge in the coming months. Many of the men who walked through Valkenburg on that September afternoon would be dead before the year ended. A plaque in Maastricht's Vrijthof square commemorates them. In Valkenburg the memory is quieter, embedded in the fact that the town survived intact enough to still have the marl houses, the gates, and the watermills you can walk past today.

Cycling decided to fall in love with Valkenburg, and Valkenburg responded by inviting it back. The town has hosted the UCI Road Cycling World Championship five times, a record, most recently in 2012. The Cauberg, that steep hill where Cuypers built his cemetery chapel, has been the finish of the Amstel Gold Race since 2003. The road climbs at gradients that turn professional racers into grimacing children. There are smaller losses too. The Wilhelminatoren, a thirty-meter viewing tower that stood atop a hill outside town and was reached by a cable car, collapsed on 16 March 2025. On 15 July 2021, the Geul river that gives the town the second half of its name overflowed and damaged bridges and buildings throughout the historic center. The town accepts these things and rebuilds. The castle has been a ruin since 1672. Permanence was never the plan.