This train bridge has been build between 1932 and 1934. It crosses 200m of the valley with 9 arches, is 5m wide and is 30m high at it's highest point and enabled the connection of Reims with Sedan and Metz by railway. The railway served to supply the Maginot defense line.
After retreat of the French defense in 1940, the Germans repaired the bridge in 1941 and removed the rails in 1943 to be used on the Eastern front.
The bridge is not in use nowadays.
Info: http://www.sud-ardennes-tourisme.com/viaduc-d-arietal/exermont/tabid/17542/offreid/fb3eb5e6-311f-4a53-819e-5819ae384a84/detail.aspx (French)