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
Medieval Corsica Nonetheless their assaults continued. In 828, the defense of Corsica was entrusted to Boniface II of Tuscany, who conducted a successful expedition against the Muslims and built the fortress that later was to bear his name (Bonifacio) in the south. For the next century, Corsica was a part of the March of Tuscany. Boniface' son Adalbert I continued to push back against the Muslim invaders after 846; but, in spite of all efforts, they seem to have remained in possession of part of the island until about 930. The island was hit by a Fatimid raid in 935. During his