In reply to peter mckenzie.

Peter, I assume you're referring to the thermal storage system - those water tanks are visible from the roof but are at ground-level.

Several of my earlier posts touch on various energy-efficient elements of the site. A good one to start with is http://blogs.cisco.com/ciscoit/data-center-constructed. I would also recommend visiting the www.cisco.com/go/dc2011 website for more information.