The entrance to the Geolide purification plant is seen in Marseille February 4, 2009. Buried 12 meters underground, beneath a bubble of futuristic glass, Geolide, which claims to be the largest such plant in the world, treats by biofiltration the 90 million cubic meters of waste water generated by the 16 communes connected to the network of the urban community of Marseille. REUTERS/Jean-Paul Pelissier (FRANCE)