Great forces have formed the caves of Wookey Hole.
The pale limestone and brownish-red conglomerate is stained vermilion with iron oxide, black with manganese, grey from the lead once mined on the Mendip Hills above.
About 400 million years ago an ocean covered this part of England.
Microscopic sea creatures swam in its waters, and their shells eventually became calcium carbonate, or limestone, which settled on the bed of the ocean to mix with and, eventually hardening into rock.
Powerful internal pressures squeezed that ocean bed like a crumpled rug to form the Mendip Hills. As the rain fell on these hills, so it began to dissolve the weaknesses in the rock, little by little widening cracks, eating into softer parts, turning into rivulets and streams.
Deep in the earth they became the River Axe. It broke through fissures in the great blocks of limestone, swirled around huge beds of the conglomerate, and worked away to enlarge the caverns, always seeking new shafts and tunnels down into the earth and eventually back into the sunlight and the distant sea.
And all the time the dissolved limestone in the water was itself reforming, creating dripping stalactites, building up great stalagmites, and turning into curtains and waterfalls of shining crystalline stone.