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
Route nationale 9 "Parc Natural Régional des Grandes Causses". After crossing the "Col d'Engayresque" (888 m) the RN 9 re-appears and drops into the Gorges du Tarn and onto Millau where the road crosses the river and climbs up to the "Causse du Larzac" offering views of the valley and viaduct. The RN 9 provides a trunk road route avoiding the toll on the Autoroute A 75 as it crosses the valley on the Viaduc de Millau. The RN 9 has again been replaced by the A 75 for this section. At the "Pas de l'Escalette" just South of Le Caylar Roches the