San Francisco, Sep 5 (IANS): Facebook has completed a new sustainable building project called "MPK 21" that has a 3.6-acre rooftop garden featuring over 200 trees and a half-mile meandering pathway.

Nestled at its headquarters in Menlo Park, California, The building has been designed to promote teamwork and allow employees to do their best work, Facebook said in a blog post late on Tuesday.

"Inside is an open workspace designed to foster collaboration between teams, as well as quiet areas for focused work," the company said.

A single pathway runs the length of the building. Along this path are five unique dining options, 15 art installations and a 2,000-person event and meeting space.

Designed by world renowned American architect Frank Gehry and built in less than 18 months, "MPK 21" encourages active engagement inside and outside of the building with pedestrian walkways, access to various outdoor areas, visible stairways, and flexible work stations.

"The reclaimed water system recycles and filter's MPK21's water and will save approximately 17 million gallons of water annually. The roof includes 1.4 MW of photovoltaic solar panels, which will generate nearly 2 million kWh of electricity annually," said By John Tenanes, Vice President, Global Facilities and Real Estate at Facebook.

Next year, Facebook plans to complete a two-acre park with a public plaza and event space, which can host its festivals, mobile farmers' market and other local programmes.