Saint-Genis-Pouilly is a commune in the Ain department in eastern France.It is located in the Pays de Gex, at the foot of the Jura. Bordering the Swiss frontier, it is part of the cross-border area of Geneva. Because of its population, it is one of the ten most important towns in the department of Ain.A large portion of CERN, the European laboratory for particle physics, is located in the territory of Saint-Genis-Pouilly; the ALICE experiment is located on the periphery of the town, and the main entrance to the primary CERN campus (Meyrin) and the ATLAS experiment are located only 3 km from the centre of St Genis. CERN is the world's largest fundamental physics research laboratory and its presence has largely been responsible for the development of the community of St Genis since the middle of the 1960s.GeographySaint-Genis-Pouilly is composed of two market towns and two hamlets . The two market towns have both continued to expand and now practically merge into one, however the two hamlets still remain separate from each other and from the two towns. The elevation of the commune varies from 419 m to 502 m . The commune is situated at the limit between the plains surrounding Geneva and the first foothills of the Jura. As indicated on the map opposite, the communes surrounding Saint-Genis-Pouilly are: Thoiry, Sergy, Crozet, Chevry, Prévessin-Moëns and Satigny .