Vaucluse Spring in Fontaine-de-Vaucluse

You're standing at the Fontaine de Vaucluse, the spring where the river Sorgue is born. Start by looking up. Above the spring towers a limestone cliff about 230 metres high, full of cracks and faults. That cliff works like a giant sponge. Rainwater soaks into it, trickles through every crevice, and only comes out again right here. And it travels a long way: from Mont Ventoux, the Vaucluse Mountains and the Albion Plateau. Together they form an underground basin of around 1,100 square kilometres, with just one way out. This one.