Plessur (river) - The Plessur is a 33 km (21 mi) long right tributary of the Rhine River running through the Swiss canton of Graubunden. The river source is near the municipality of Arosa in the Plessur Range. It then flows through the Schanfigg valley before emptying into the Rhine at Chur.The Langwieser Viaduct an early reinforced concrete railroad bridge constructed in 1914 spans the Plessur near the municipality of Langwies. Given a choice of categories company, educational institution, artist, athlete, office holder, mean of transportation, building, natural place, village, animal, plant, album, film or written work, the text refers to which one?
A:
Natural Place