Being a city on the Ill and close to the Rhine, Strasbourg has always been an important centre of fluvial navigation, as is attested by archeological findings. In 1682 the Canal de la Bruche was added to the river navigations, initially to provide transport for sandstone from quarries in the Vosges for use in the fortification of the city. That canal has since closed, but the subsequent Canal du Rhone au Rhine, Canal de la Marne au Rhin and Grand Canal d'Alsace are still in use, as is the important activity of the Port autonome de Strasbourg. Water tourism inside the city proper attracts hundreds of thousands of tourists yearly.