river, north central France, navigable tributary of the Seine, which it joins above Romilly. The Aube and its tributary, the Aujon, rise on the Langres Plateau, flowing northwest for 154 mi (248 km) in trenchlike valleys across the dry oolitic limestone country. In front of the Côte des Bars escarpment, the valleys open out as stone gives way to clay at Montigny-le-Roi and Châteauvillain. As they enter the Aube département the two rivers join at Clairvaux. Moving toward Brienne, the river receives many small tributaries. After it passes Brienne on its way to the Seine, few surface tributaries add to the volume, and the country is flat alluvial earth on the Champagne chalk platform.