Corsica is in the Tyrrhenian Sea in the western Mediterranean, 160 km (100 miles) south-west of the French Riviera and 82 km (50 miles) west of the coast of Tuscany, on the same latitude as Rome – Italy. Often known as the Mountain in the Sea, the highest point is Monte Cintu at 2.710 m (8,900'), and there are twenty other mountains of over two thousand metres and an average altitude of 560m.

The GR 20 is a footpath that crosses the island of Corsica running approximately north-south, described by the outdoor writer Paddy Dillon as « one of the top trails in the world ».