Now: A large swath of the eastern side of the Presidio (bordering the Marina) has been redeveloped as a grassy park adjacent to office complexes. Very twisty roads fill the middle area, through gorgeous wooded areas and streets lined with former military housing. The west side meets the Pacific Ocean and encompasses the popular Baker Beach and some scenic battery installments leading north toward the Golden Gate Bridge.
Then: A base for the U.S. military since 1846 (and Spain and Mexico prior to that, dating back to 1776), the Presidio was turned over to the public under the Presidio Trust (created by the U.S. government to manage the property) in 1996. Since then, the buildings that formerly housed military personnel have been leased for use by businesses and residences.
How To Get There: Some Muni bus lines do run through the Presidio, though mostly around the perimeter and toward Golden Gate Bridge. The east side of the Presidio, including the recently developed park area, can easily be entered from Chestnut Street, or any street on the west edge of the Marina. The scenic areas on the west side can be reached by entering at 25th Avenue, which turns into Lincoln Boulevard. Mountain Lake Park can be entered from Lake Street at 12th Avenue.

Presidio, on the east side, near Lincoln Boulevard

Presidio building on Funston Avenue, near Lincoln Boulevard

East side of the Presidio, facing the Palace of Fine Arts

Fountain near the eastern edge of the Presidio

Pres a Vi Restaurant and Wine Bar, at the intersection of Lombard Street and Letterman Drive in the Presidio

Chestnut Street entry to the Presidio

Houses on Storey Avenue in the Presidio

Log Cabin, built in 1937, on Storey Avenue in the Presidio

Inspiration Point, where Arguello Boulevard intersects with Washington Boulevard in the Presidio

Baker Beach, at the end of Gibson Road, off of Lincoln Boulevard at the west edge of the Presidio

West toward the ocean, from Baker Beach

Baker Beach, north view toward Golden Gate Bridge

Baker Beach

Picnic tables in the park grounds at Baker Beach

Battery Godfrey, at Langdon Court, off Lincoln Boulevard on the northwest edge of the Presidio

Pacific Ocean, from the cliff edge at Battery Godfrey

View from Battery Godfrey, toward Golden Gate Bridge

Walking path at Battery Godfrey

Ocean view from the edge of Battery Godfrey

Concrete structure at Battery Godfrey

North view, from Battery Boutelle

Battery Cranston, near the Golden Gate Bridge in the Presidio

Cliffs near the Coastal Trail, south of the Golden Gate Bridge

Coastal Trail at the west edge of the Presidio, leading toward the Golden Gate Bridge

Looking south from the cliffs near the Coastal Trail

Ocean surf at the bottom of the cliffs near the Coastal Trail

Looking south on the Coastal Trail near the Golden Gate Bridge

The west side of the Presidio, near the ocean

Mountain Lake Park, at the south edge of the Presidio

Entrance to Mountain Lake Park, at Lake Street and 12th Avenue

Playground at Mountain Lake Park

Mountain Lake Park

Walkway in Mountain Lake Park, leading out to Lake Street

Plaque marking camp site of colonists in Mountain Lake Park

Walking path on the north edge of the lake, in Mountain Lake Park

Benches at the north edge of Mountain Lake Park