Vexin (French pronunciation: [vɛksɛ̃]) is an historical county of northwestern France. It covers a verdant plateau on the right bank (north) of the Seine running roughly east to west between Pontoise and Romilly-sur-Andelle (about 20 km from Rouen), and north to south between Auneuil and the Seine near Vernon. The plateau is crossed by the Epte and the Andelle river valleys. Source: Wikipedia (en)