San Francisco is the fourth most populous city in California and the 12th most populous city in the United States, with a 2008 estimated population of 808,976. It is the eighth most densely populated city in the U.S. and is the financial, cultural, and transportation center of the larger San Francisco Bay Area, a region of more than seven million people. The city is located at the northern end of the San Francisco Peninsula, with the Pacific Ocean to the west and San Francisco Bay to the north and east, and Daly City and Brisbane to the south.

Today, San Francisco is a popular international tourist destination renowned for its chilly summer fog, steep rolling hills, eclectic mix of Victorian and modern architecture and its famous landmarks, including the Golden Gate Bridge, the cable cars, and Chinatown.

Geography
San Francisco is located on the West Coast of the United States at the tip of the San Francisco Peninsula and includes significant stretches of the Pacific Ocean and San Francisco Bay within its boundaries. Several islands—Alcatraz, Treasure Island, and the adjacent Yerba Buena Island, and a small portion of Alameda Island, Red Rock Island, and Angel Island are part of the city. Also included are the uninhabited Farallon Islands, 27 miles (43 km) offshore in the Pacific Ocean. The mainland within the city limits roughly forms a "seven-by-seven-mile square," a common local colloquialism referring to the city's shape, though its total area, including water, is nearly 232 square miles (600 km2).

San Francisco is famous for its hills. There are more than 50 hills within city limits. Some neighborhoods are named after the hill on which they are situated, including Nob Hill, Pacific Heights, and Russian Hill. Near the geographic center of the city, southwest of the downtown area, are a series of less densely populated hills. Twin Peaks, a pair of hills resting at one of the city's highest points, forms a popular overlook spot. San Francisco's tallest hill, Mount Davidson, is 925 feet (282 m) high and is capped with a 103 foot (31 m) tall cross built in 1934. Dominating this area is Sutro Tower, a large red and white radio and television transmission tower.
The San Andreas and Hayward Faults are responsible for much earthquake activity, even though neither passes through the city itself. It was the San Andreas Fault which slipped and caused the earthquakes in 1906 and 1989. Minor earthquakes occur on a regular basis. The threat of major earthquakes plays a large role in the city's infrastructure development. The city has repeatedly upgraded its building codes, requiring retrofits for older buildings and higher engineering standards for new construction. However, there are still thousands of smaller buildings that remain vulnerable to quake damage.
San Francisco's shoreline has grown beyond its natural limits. Entire neighborhoods such as the Marina and Hunters Point, as well as large sections of the Embarcadero, sit on areas of landfill. Treasure Island was constructed from material dredged from the bay as well as material resulting from tunneling through Yerba Buena Island during the construction of the Bay Bridge. Such land tends to be unstable during earthquakes; the resultant liquefaction causes extensive damage to property built upon it, as was evidenced in the Marina district during the 1989 Loma Prieta earthquake.

Neighborhoods
The historic center of San Francisco is the northeast quadrant of the city bordered by Market Street to the south. It is here that the Financial District is centered, with Union Square, the principal shopping and hotel district, nearby. Cable cars carry riders up steep inclines to the summit of Nob Hill, once the home of the city's business tycoons, and down to Fisherman's Wharf, a tourist area featuring Dungeness crab from a still-active fishing industry. Also in this quadrant are Russian Hill, a residential neighborhood with the famously crooked Lombard Street, North Beach, the city's Little Italy, and Telegraph Hill, which features Coit Tower. Nearby is San Francisco's Chinatown, established in the 1860s. The Tenderloin is frequently described as the worst neighborhood in the city by tourist guides.
The Mission District was populated in the 19th century by Californios and working-class immigrants from Germany, Ireland, Italy and Scandinavia. In the 1910s, a wave of Central American immigrants settled in the Mission and, in the 1950s, immigrants from Mexico began to predominate. Recent years have seen rapid gentrification primarily along the Valencia Street corridor which is strongly associated with modern hipster sub-culture. Haight-Ashbury, famously associated with 1960s hippie culture, later became home to expensive boutiques and a few controversial chain stores, although it still retains some bohemian character. Historically known as Eureka Valley, the area now popularly called the Castro is the center of gay life in the city.

The city's Japantown district suffered when its Japanese American residents were forcibly removed and interned during World War II. The nearby Western Addition became established with a large African American population at the same time. The "Painted Ladies," a row of well-restored Victorian homes, stand alongside Alamo Square, and the mansions built by the San Francisco business elite in the wake of the 1906 earthquake can be found in Pacific Heights. The Marina to the north is a lively area with many young urban professionals.
The Richmond, the vast region north of Golden Gate Park that extends to the Pacific Ocean has a portion called "New Chinatown" but is also home to immigrants from other parts of Asia and Russia. South of Golden Gate Park lies the Sunset with a predominantly Asian population. The Richmond and the Sunset are largely middle class and, together, are known as The Avenues. These two districts are each sometimes further divided into two regions, the Outer Richmond and Outer Sunset can refer to the more Western portions of their respective district and the Inner Richmond and Inner Sunset can refer to the more Eastern portions. Bayview-Hunters Point in the southeast section of the city is one of the poorest neighborhoods and suffers from a high rate of crime, though the area has been the focus of controversial plans for urban renewal.
The South of Market, once filled with decaying remnants of San Francisco's industrial past, has seen significant redevelopment. The locus of the dot-com boom during the late 1990s, by 2004 South of Market began to see skyscrapers and condominiums dot the area (see Manhattanization). Following the success of nearby South Beach, another neighborhood, Mission Bay, underwent redevelopment, anchored by a second campus of the University of California, San Francisco. Just southwest of Mission Bay is the Potrero Hill neighborhood featuring sweeping views of downtown San Francisco.

Beaches and parks
Ocean Beach runs along the Pacific Ocean shoreline and is frequented by surfers, but few others swim there because the waters off the coast are perennially cold and form dangerous rip currents. Baker Beach is located in a cove just inside the Golden Gate and next to the Presidio, a former military base. Crissy Field, within the Presidio, has been restored to its natural salt marsh ecosystem. All of these together, plus other sites such as Alcatraz, Lands End, and Fort Funston, form part of the Golden Gate National Recreation Area, a regional collection of beaches, parks, and historic sites administered by the National Park Service. The NPS separately administers the San Francisco Maritime National Historical Park—a fleet of historic ships and waterfront property around Aquatic Park.
There are more than 200 parks maintained by the San Francisco Recreation and Parks Department. The largest and best-known city park is Golden Gate Park, which stretches from the center of the city west to the Pacific Ocean. Once covered in native grasses and sand dunes, the park was conceived in the 1860s and was created by the extensive planting of thousands of non-native trees and plants. The large park is rich with cultural and natural attractions such as the Conservatory of Flowers, Japanese Tea Garden and San Francisco Botanical Garden. Lake Merced is a fresh-water lake surrounded by parkland and near the San Francisco Zoo, a city-owned park which houses more than 250 animal species, many of which are designated as endangered. The only park managed by the California State Park system located principally in San Francisco, Candlestick Point was the state's first urban recreation area.