GRAMMAR'S RESPONSE. The word premises is always plural, whether you're referring to the whole of the land and the buildings upon it or just part of the mall (or whatever). So you want are, always. Authority: Merriam-Webster's Collegiate Dictionary, Electronic Edition, Version 1.5.
Yonne is a department in the centre of France, in the Burgundy region. The largest city in the department, and its prefecture (capital), is Auxerre.
Orsay is situated in the Essonne, Paris region, in the Paris region of France at 20 km from Evry, the department capital. (General information: Orsay is 21 km from Paris). Popular places to visit nearby include Versailles Palace at 13 km and Paris at 21 km. For more places to visit and local tourist attractions see the map and listings below.