he talked of the beauty and the treachery of venice , of the city 's dedication to moneymaking , of its richesse , its weird construction - a city of canals rising out of fenland and built on a foundation of hundreds of thousands of huge wooden stakes - its ferocious independence , and its political power : not three hundred years earlier , the doge of venice had diverted an entire crusade from the holy land to serve his own purposes , to destroy all commercial and military competition and opposition to his city-state , and to bring the byzantine empire to its knees .