Basque countryside like a step back in time

I’M NOT especially claustrophobic but we are heading deeper and deeper into the bowels of the mountain under thousands of tons of rock and my inner Chilean miner is making itself known to me.
Liliana, our chaperone, whispers furtive translations of our guide’s Spanish-only monologues but he’ll brook no interruption and barks at her until she dries up save for the occasional muttered aside. On we trek until the passage opens up into a great big cathedral of a cavern, a crossroads branching off to several different tunnels. Our guide points to a near vertical face stretching up to a chimney disappearing into darkness. He barks out a few words. Liliana whispers: “This is where Tito Bustillo and his friends entered the cave system.” We trudge onwards, sometimes on rock worn smooth by underground rivers, sometimes on loose scree, crossing trickling streams until we reach our destination. Our guide rattles on for a goodly spell, flashing torch hither and thither illuminating only more cave. He switches to an ultra-violet beam, training it on a wall close to where I stand. And there they are — horses, beautifully rendered in tones of umber, ochre and violet.