Venice, December 13 - Public works officials in Venice said on Thursday that restoration of the Rialto Bridge that crosses the city's Grand Canal will be carried out by Otb, a company headed by Renzo Rosso, founder and owner of the Diesel clothing brand. Rosso, whose company is based in the Veneto region, has long been rumored as an eager donor to restore the 400-year-old landmark. The complete restoration will cost five million euros and is expected to take 18 months. Rosso's Otb was the only bidder for the works needed to preserve the World Heritage Site. An estimated 20 million tourists trample Venice's ancient pavement every year, inevitably taking a toll on the Rialto Bridge, a city icon that for centuries was the only foot passage from one side of the Grand Canal to the other. Last year a column on the bridge's railing collapsed, and some of the marble steps have begun to crack, one of which was dislodged last summer, closing down part of the bridge. Calls for donors have become increasingly common as city budgets have been cut amid Italy's economic crisis. Last year Diego Della Valle, the founder of the luxury leather goods brand Tod's, announced he was investing over 25 million euros in the three-year restoration of Rome's Colosseum, enlisting further help from the Italian business community to bankroll restoration and conservation plans elsewhere in the country in the absence of government support. The most visible example is French luxury-fashion mogul Francois Pinault, owner of such lines as Gucci, Balenciaga and Stella McCartney. Pinault made a splash in the Venice lagoon with the purchase of Palazzo Grassi, followed by the acquisition and restoration of the landmark Punta della Dogana, both of which house his personal art collection as well as featuring major exhibitions. Other fashion labels restoring sites in Venice include Bulgari, Replay and Palazzetti, in addition to Prada and Benetton who have recently bought palaces on the Grand Canal for private use.