Corsica and killings culminated in the assassination of Prefect Claude Érignac in 1998. In 2013, Corsica hosted the first three stages of the 100th Tour de France, which passed through the island for the first time in the event's 110-year history. 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
Corsica French from the island and established an Anglo-Corsican Kingdom. Following Spain's entry into the war, the British decided to withdraw from Corsica in 1796. Corsica returned to French rule. Despite being the birthplace of the Emperor, who had supported Paoli in his youth, the island was neglected by Napoleon's government. In 1814, near the end of the Napoleonic Wars, Corsica was briefly occupied again by British troops. The Treaty of Bastia gave the British crown sovereignty over the island, but it was later repudiated by Lord Castlereagh who insisted that the island should be returned to a restored French monarchy.