Located in Limburg, the southernmost province of the Netherlands, Valkenburg, a marlstone hamlet nestled amid moss-green hills in the heart of the 'Heuvelland' nature reserve, is the country's oldest tourist destination and one of the few places in the country with actual mountains. It has been a landmark for nearly 130 years with its undulating terrain and picturesque surroundings, as well as its two major attractions - the famed castle ruins and marlstone caves. Even though just the remains of Castle Valkenburg exist, it is nonetheless worth a visit because it is the country's only castle built on a hill and therefore offers a panoramic view of the city from its broken ramparts.