From http://en.wikipedia.org/wiki/Twin_Peaks_(San_Francisco,_California) :
The peaks each have their own names: Eureka Peak/North Peak and Noe Peak/South Peak. 100 ft below the Eureka/North Peak is the popular vista point known locally as ‘Christmas Tree Point’, which offers unobstructed views of most San Francisco and the San Francisco Bay.
To the north sits one of the city’s many reservoirs. It is owned by the San Francisco Fire Department, and supplies water to the Fire Department’s independent HPFS water system for fighting fires, established after the 1906 earthquake and fire.
The summit of Twin Peaks remain mostly undeveloped. They were designated as part of the 31 acres (130,000 m2) Twin Peaks Natural Area, managed and owned by the San Francisco Recreation and Parks Department. These preserved areas are home to many natural resources and wildlife. As part of the Mission blue butterfly habitat conservation, Twin Peaks is one the few remaining habitats for this endangered species. A wide variety of bird species, insects and vegetation also thrive in these areas.
The Muni Metro Twin Peaks Tunnel runs beneath the Twin Peaks, linking Downtown San Francisco with West Portal and the southwestern part of the city. There is no public transportation service directly to the summit of the Peaks, but the 37 Corbett Muni line stops near a path that runs up the hills on Crestline Drive.
The San Francisco Police Department Academy is located at the base of the mountain range.
The name ‘Twin Peaks’ is also applied to the surrounding neighborhood.