This is an advanced script Written in python to let you easily create a complex environment with maintaining the memory you can create scenes with 150 million polygons very easy just use the power of instancing
you can download it from the easy environment script from creativeCrash.com
http://www.creativecrash.com/maya/marketplace/scripts-plugins/rendering/other-renderers/c/easy-environment
3d environment
Full Description for Easy Environment