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
The Biggest Little Railway in the World cross the canal at Laggan . The A82 road at this point uses a swing bridge and it was determined The Biggest Little Railway in the World would not use this. The solution was to use a truss bridge. The bridge was later re-used at the Caledonian Helix. Crossing the Aberchalder Spillway , which was bridged with a viaduct. The team are outraged when Dick Strawbridge insists the Battery Electric "Little John" relief locomotive is used for the iconic crossing. The feature initially seems to have variously termed a "ford" or a "weir" by the project whereas "spillway" seems correct,