Its affluents are, on the right, the Aube; the Marne, which joins the Seine at Charenton near Paris; the Oise, which has its source in Belgium and is enlarged by the Aisne; and the Epte; on the left the Yonne, the Loing, the Essonne, the Eure and the RUle.
Colsa, grown chiefly in the lower basin of the Seine (SeineInfrieure and Eure), is the most important of the oil-producing plants, all of which show a diminishing acreage.
The northern part of Eure-et-Loir is watered by the Eure, with its tributaries the Vegre, Blaise and Avre, a small western portion by the Huisne, and the south by the Loir with its tributaries the Conic and the Ozanne.
Chartres is built on the left bank of the Eure, on a hill crowned by its famous cathedral, the spires of which are a landmark in the surrounding country.
The Eure, which at this point divides into three branches, is crossed by several bridges, some of them ancient, and is fringed in places by remains of the old fortifications, of which the Porte Guillaume (14th century), a gateway flanked by towers, is the most complete specimen.
