Genoa, the capital of Liguria, stretches along the bay of the same name from Voltri to the west as far as Nervi to the east, while the hinterland area takes in the lower parts of the Polcevera and Bisagno Valleys.The present-day urban conglomeration is the result of the merging of various municipalities in 1926. The original nucleus of the city, which already existed in pre-Roman times, developed around the Mandraccio wharf area and on Castello Hill, which overlooks it. In the ninth century, the Genoese built the first town walls and laid the foundations for the development of shipping and sea-trading, which would eventually make the Republic of Genoa a Mediterranean sea power and create a dominion stretching across the entire region of Liguria. From the nineteenth century onwards, the great city port was flanked by large industrial areas. The old town district is one of the largest in Europe.