Genuine prehistoric caves can still be visited just outside the attractive village of PUENTE VIESGO, set in a river gorge amid magnificent forested escarpments on the N623 to Burgos, 15km southeast of Santillana or 24km southwest of Santander. Guided tours (in Spanish only) depart from an informative visitor centre located 1.5km up a winding mountain road from the village bus stop (served by SA Continental buses from the main station in Santander). Two of the four caves, 700 metres apart, are open to the public, Las Monedas and the slightly better El Castillo, but places are limited, and in summer it’s best to book at least 24 hours in advance. The caves are magnificent, with weirdly shaped stalactites and stalagmites, and bizarre organ-like lithophones, natural features used by Paleolithic peoples to produce primitive music, while the astonishing paintings, depicting animals from mammoths to dogs, are clear precursors to the later developments at Altamira. Should you be unable to find a place on a tour, the visitor centre has an excellent digital exhibit enabling 360-degree views and interactive “tours”.