The Velvet Cave had been closely related to the rich history of Valkenburg's Castle Ruins. Its origin can be traced back in the 11th and 12th centuries, when marl stones were excavated for the construction of the Valkenburg Castle. The digging up and excavation of marl stones resulted in an extensive labyrinth of craggy tunnels. During different wars, through secret escape routes from the castle to these tunnels, knights and war armies can leave the sieged castle unseen and to strategically attack the enemies from the back door. It wasn't until 1937, during the restoration of the castle, when it was discovered. Many of the existing stone walls tell a story of the past through charcoal drawings and sculptures created at different times. The year-round dry and cooler temperatures (12 deg C or 53 deg F) preserved the authenticity of most of the drawings. During World War II, the cave also served as a refuge for the people of Valkenburg and a hideout for the American soldiers. Additional visitation tip: Take a tour of the castle prior visiting the cave to get an idea of its scale (see http://www.trover.com/d/1f0fQ-valkenburg-castle-ruins-valkenburg-netherlands). It's totally dark inside the cave, a guide will provide lamp to easily navigate through the tunnels. Some sections have dim lighting which automatically turns on and off as you go through it. How to get here: Valkenburg is situated in the south of Netherlands, and only less than 10 miles east of Maastricht. It can be reached by a local bus transit from Maastricht within 30 minutes. Maastricht connects to a huge rail network in and outside Netherlands. #InStone