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
Geology of the Massif Central from the main basement outcrops. In general the Massif Central is an asymmetric basement plate elevated at its southern margin by the Pyrenees orogeny and along its eastern margin by the Alpine orogeny. Along these margins it descends very abruptly to the surrounding grabens. These margins also show the highest elevations, the plate being gently inclined to the Northwest where the basement rocks disappear under the Mesozoic cover of the Aquitaine basin and the Paris Basin. This somewhat simplistic model is locally disturbed by fault lines and graben structures – for instance the massif's highest elevation is positioned in the