The Calpine Geothermal Visitor Center is located in Middletown, California, about 70 miles (113 km) north of San Francisco. It is a single-story, 6,000 ft2 (560 m2) building and is the visitor center for The Geysers geothermal field, the largest geothermal power generating operation in the world. The visitor center building has incorporated a number of “green” features, one of which is a geothermal heat pump system. Completed in 2001, the building has a lobby area, an exhibit hall featuring geothermal power displays, small offices, a conference room, a kitchen, and a multipurpose room