Chioggia is situated on a small island at the southern entrance to the Lagoon of Venice about 25 kilometres (16 miles) south of Venice (50 km (31 mi) by road); causeways connect it to the mainland and to its frazione, nowadays a quarter, of Sottomarina. The population of the comune is around 50,000, with the town proper accounting for about half of that and Sottomarina for most of the rest. The municipality, located in south of the province, close to the provinces of Padua and Rovigo, borders with Campagna Lupia, Cavarzere, Codevigo, Cona, Correzzola, Loreo, Rosolina and Venice. Chioggia is a miniature version of Venice, with a few canals, chief among them the Canale Vena, and the characteristic narrow streets known as calli. Chioggia has several medieval churches, much reworked in the period of its greatest prosperity in the 16th and 17th centuries. The church of S. Maria, founded in the eleventh century, became a cathedral in 1110, then was rebuilt as Chioggia Cathedral from 1623 by Baldassarre Longhena.