Puente Viesgo has the strange distinction of being a Cantabrian village of about two and a half thousand people that sits under one of the most important prehistoric hills in Europe. Monte Castillo is a steep, cone-shaped limestone mountain beside the River Pas, and it is riddled with caves. La Pasiega is one of four that have been explored and painted on a grand scale, the others being El Castillo, Las Chimeneas and Las Monedas. Together they form a small campus of Ice Age art, and people travel from across the world to look at them.
La Pasiega takes its name from the Pas valley and its cattle-herding pasiegos, the mountain people who have kept cows on these hills for centuries. Inside, the cave is a series of galleries and side passages decorated with red and black paintings of horses, deer, bison and ibex, along with signs, grids and dots whose meaning is still debated. It is one of the Cantabrian caves where the old question of Neanderthal art keeps coming up, as new dating work has been attempted on some of the red marks in this part of Spain. Treat any firm claim with a pinch of salt; it is a lively argument.
Visits are by guided group only, with strictly limited numbers to protect the air and the paintings, so book ahead online or by phone, especially in summer and around Easter. There is a modern visitor centre at the foot of the hill, where you can learn about the caves before going up.
The ride itself is classic Cantabria. The N-623 climbs from Santander country through Puente Viesgo and Santiurde de Toranzo toward the Puerto del Escudo, with green meadows, small stone villages, and a mountain pass that sweeps over into Burgos. Expect cooler weather and mist in the morning; Cantabria is a wet corner of Spain and the road can be damp even when the sky looks clear.
Fuel and food are straightforward. Puente Viesgo has bars and a few small restaurants, and Los Corrales de Buelna, nine kilometres away, is the larger town for pumps. Try a cocido montañés or a sobao, the local butter sponge, if you want something local.