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
Stone Bridge and the Oregon Central Military Wagon Road to pass over it. The Army abandoned the crossing in 1874 when it closed Fort Warner and left the area. In the meantime, the Oregon Central Military Wagon Road had begun using the Stone Bridge to cross the Warner Lakes. However, the road company never maintained it. After the military road was abandoned, local ranchers used the causeway as a cattle crossing for many years. Eventually, the causeway settled into the soft marshy ground, disappearing beneath the water. Today, the Stone Bridge is completely underwater except during periods of drought. As a result, it is very difficult to find. Between