Proper noun
Yvelines pl (plural only)
One of the departments of Île-de-France, France. Capital: Versailles (INSEE code 78).
Waterlooville is twinned with Maurepas, Yvelines in France and Henstedt-Ulzburg in Germany. Source: Internet
Versailles was made the préfecture of the Yvelines département, the largest chunk of the former Seine-et-Oise. Source: Internet