Altamira Caves
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. Only 5 visitors are allowed into the caves each week, and entrance is determined by a lengthy waiting list. The reproduction in the museum, however, is open to all.