3 Best Sights in Galicia, Asturias, and Cantabria, Spain

These world-famous caves, 3 km (2 miles) southwest of Santillana del Mar, have been called the Sistine Chapel of prehistoric art for the beauty of their drawings, believed to be some 18,000 years old. First uncovered in 1875, the caves are a testament to early mankind's admiration of beauty and surprising technical skill in representing it, especially in the use of rock forms to accentuate perspective. The reproduction of the caves in the museum is open to all. Only five visitors a week can visit the original caves, and entrance is determined by a lengthy waiting list and lottery.

In 1903, four caves were discovered in this 16th-century hamlet in the Pas Valley, under the 350-meter (1,150-foot) peak of Monte del Castillo. Two of these—Cueva del Castillo and Cueva de las Monedas—are open to the public. Bison, deer, bulls, and humanoid stick figures are depicted within the caves; the oldest designs are thought to be 35,000 years old. Most arresting are the paintings of over 50 hands (some 35 of them remain). The painters are thought to have blown red pigment around their hands through a hollow bone, leaving the negative image. Online reservations are essential.

Discovered in 1968, the cave here has 20,000-year-old paintings on a par with those in Lascaux, France, and Altamira. Giant horses and deer prance about the walls. To protect the paintings, no more than 150 visitors are allowed inside each day, so reservations are essential. The guided tour is in Spanish. There's also a museum of Asturian cave finds, open year-round. Audio guides for the museum are available in English.