Kerstmarkt Fluweelengrot Valkenburg

Somewhere above your head, through the rock, are the ruins of Valkenburg castle. That is not a coincidence. The passages you are walking through were cut to build it.

From around the year 1050, people quarried the soft yellow marl out of this hill, block by block, and carried it up to raise the castle walls. The tunnels kept growing for eight centuries. Together they run for about five kilometres. Local stories say the knights used them as secret escape routes, slipping out of the castle unseen and coming up behind an attacking army.

Mining stopped around 1886, and the passages were forgotten. But they had already been a hiding place more than once. In 1797, during the French occupation, Napoleon's government closed the churches and exiled priests who refused to swear loyalty to France. A priest called Father Widdershoven built a secret chapel deep in these tunnels and kept saying Mass here.

The passages were rediscovered in 1937, just in time. During the Second World War the cave sheltered Jewish people, local families and, later, American soldiers. Look at the walls as you go: some of those soldiers carved their names into the marl.

It is about twelve degrees in here, all year round, and very damp. That is why this market feels the way it does. You are not under a tent. You are inside a quarry that has kept people safe for a thousand years.