Corsica was formed about 250 million years ago with the uplift of a granite backbone on the western side. About 50 million years ago sedimentary rock was pressed against this granite, forming the schists of the eastern side. It is the most mountainous island in the Mediterranean, a "mountain in the sea".It is also the fourth largest island in the Mediterranean, after Sicily, Sardinia and Cyprus.

It is 183 kilometres (114 mi) long at longest, 83 kilometres (52 mi) wide at widest, has 1,000 kilometres (620 mi) of coastline, more than 200 beaches, and is very mountainous, with Monte Cinto as the highest peak at 2,706 metres (8,878 ft) and around 120 other summits of more than 2,000 metres (6,600 ft). Mountains comprise two-thirds of the island, forming a single chain. Forests make up 20% of the island. (Wikipedia)