summer evenings. A bit more to the north is located the commercial and ferry port. As a major economic asset of the city, the "port de commerce" is the pulse of the city. It is even more so during the summer when ferry arrivals and departures of thousands of passengers and cars can sometimes cause long traffic jams along the north–south axis, the national road RN193. In front of the commercial port, the large Saint-Nicolas square represents the heart of the city. Just north of the commercial port, the Toga marina, named after a city neighborhood, is a harbor for leisure boating activities like sailing and yachting. There are also some bars, restaurants and night clubs on its docks. Thus, Bastia is organized on a relatively narrow north–south axis which can make access to the city centre difficult under particular circumstances. Nowadays, the city centre is mainly composed of the "citadelle", the stronghold, also called Terra-Nova, with the Genoese Governors' Palace, the old port and port quarter and the market plaza, and finally the ensemble of buildings along the "Boulevard Paoli", the main commercial street of the city, which lies from the Justice Court to the Avenue Maréchal Sebastiani. During the last few decades, Bastia and its region have experienced a strong demographic growth, which has caused somewhat of a suburban crawl in the south of the city, because of the congestion of the city center. Geology and relief The commune is located in the Alpine Eastern Corsica region which is formed from "a succession of autochthons (fixed terrain), para-autochtons (weakly displaced terrain) and especially allochthons (highly displaced terrain). The first two coincide roughly with the central depression. The allochhtons are mainly in the area of lustrous schists and ophiolites corresponding to the eastern relief (Cap Corse and Castagniccia)". Its base rests on a granite bedrock (Felsic granites from the Hercynian, plain rocks), which has been covered with oceanic layers of: Sedimentary rocks (Miocene to Quaternary) on the east coast, ranging from the mouth of the Ruisseau de Lupino north to the south bank of the mouth of the Travo lustrous schists along the entire eastern side of Cap Corse, ophiolite deposited in eastern Corsica during the Eocene period. Note the presence of copper ore in Cardo which was once the subject of a concession. Geographically, Bastia is characterized by its location between the sea and the mountains. The commune