The Grand Canal is a canal in Venice, Italy. It forms one of the major water-traffic corridors in the city. Public transport is provided by water buses vaporeti and private water taxis, and many tourists explore the canal by gondola. One end of the canal leads into the lagoon near the Santa Lucia railway station and the other end leads into Saint Mark Basin; in between, it makes a large reverse-S shape through the central districts (sestieri) of Venice. It is 3.8 km long, and 30 to 90 m wide, with an average depth of five meters (16.5 ft). The banks of the Grand Canal are lined with more than 170 buildings, most of which date from the 13th to the 18th century, and demonstrate the welfare and art created by the Republic of Venice. The Grand Canal probably follows the course of an ancient river flowing into the lagoon. Adriatic Veneti groups already lived beside the formerly-named "Rio Businiacus" before the Roman age. They lived in stilt houses and depended on fishing and commerce (mainly salt). Under the rule of the Roman empire and later of the Byzantine empire the lagoon became more populated and important, and in the early 9th century the Doge moved his seat from Malamocco to the safer "Rivoaltus". Increasing trade followed the Doge and would find in the deep Grand Canal a safe and ship accessible canal-port. Drainage reveals that the city became more compact over time: at that time the Canal was wider and flowed between small, tide-subjected islands connected by wooden bridges.