Tarn (river) a mean flow of approximately . The Millau Viaduct spans the valley of the Tarn near Millau, and is now one of the area's most popular attractions. The tributaries of the Tarn include: The Tarn separates the Narbonne and Aquitaine basins. The Tarn passes through the following departments and towns: The Millau Viaduct, the tallest bridge in the world, carrying the A75 autoroute across the Tarn Gorge near Millau, opened in December 2004. The Tarn is famous for its brutal floodings, which are the most dangerous in Europe along with the Danube. The flooding of March 1930 saw the Tarn
Millau Viaduct is direct and without tolls for the between Clermont-Ferrand and Pézenas, except for the bridge itself. The Eiffage group, which constructed the Viaduct, also operates it, under a government contract, which allows the company to collect tolls ("Péage") for up to 75 years. As of 2018, the toll bridge costs €8.30 for light automobiles (€10.40 during the peak season of 15 June to 15 September). Each of the seven pylons is supported by four deep shafts, deep and in diameter. The abutments are concrete structures that provide anchorage for the road deck to the ground in the Causse du Larzac