San Francisco is a city of neighborhoods, due to its topography and man-made demarcations. Each has its own vibe, a collective personality that makes traversing the city as a tourist an intriguing adventure and provides fresh discoveries for locals exploring their own city. And they are many, some only a few blocks long, microcosms of a larger district, others quite large.  Some of the largest and well-known to travelers are mentioned here.

In addition to its history of rebellion, one of the great hallmarks of San Francisco is its remarkable diversity. While half of the city’s growth during the 19th century was due to the arrival of American emigrants, the balance was due to immigration from around the world. Today, the city reflects this fact with its cosmopolitan flair and distinct ethnic neighborhoods.

At one time, one of the largest Chinese populations outside of Asia could be found in the heart of San Francisco. Chinatown spans several city blocks and is alive with live fish markets, produce stands, tourist stores, jewelry stores, fortune tellers, temples and restaurants. Next door you will find North Beach, an Italian enclave where the Chinese once were not allowed to cross into, packed with cafes, excellent restaurants and, in a nod to the days of the Barbary Coast, a  handful of the strip clubs. These were the clubs that first scandalized visitors with their topless -- then bottomless" -- dancers, the most famous of which was Carol Doda, who merited her own cartoonish likeness on the marquee of the Condor Club, prominently flashing with lights, right at Broadway and Columbus Avenue.

Southwest of these neighborhoods is the Mission District, home to recent immigrants from Latin America and recent college graduates. This lively, multi-cultural neighborhood contains cool hipster lounges, wandering musicians who will play for pay, and impressive street murals.

Two of the most well-known neighborhoods in San Francisco, are the Castro and Haight-Ashbury. The Castro is San Francisco's Gay community center and cultural heart, where Harvey Milk was elected to the Board of Supervisors, and where one of the largest Pride celebrations in the country takes place,  a major tourist draw and a boon to the city in mid-June. The Haight is the place where young, long-haired people flocked during the 1967 Summer of Love. If you were going to San Francisco, as the song goes, "be sure to wear some flowers in your hair.''  Look closely and you might find the places where Jerry Garcia and Janis Joplin crashed.

For the ritzier side of San Francisco, check out the mansions perched on the steep hills of Pacific Heights and Presidio Heights.  You can cruise the neighborhoods of the likes of Danielle Steele and Gordon Getty, not to mention the cool digs of movie stars like Robin Williams. Down the hill towards the Bay, you’ll find Cow Hollow, which offers great shops on Union Street.  The Marina also offers great shops and restaurants on Chestnut Street and borders the Presidio and the Golden Gate Bridge - explore the neighborhood, then walk out to the bridge for great views of the Bay (and Alcatraz!). Heading down the hill in the opposite direction, look for the Fillmore District , and Japantown, filled with shops, restaurants and movie theater.

For an eclectic experience, try either Hayes Valley or South of Market (SoMa)The New York Times called Hayes Valley the "NoLiTa" (of New York) of San Francisco, chock full of  designer boutiques, art galleries, funky shoe stores, and great restaurants, an area that once languished in the shadow of the Central Freeway, and blossomed once the freeway was pulled down.  Hayes Valley is just west of the Civic Center area (where City Hall, the opera, symphony, and ballet are located), and as such, very central. It's a great starting or stopping point on a walking tour of all of those neighborhoods.  Many people like to shop or eat in Hayes Valley before or after seeing a show in the Civic Center area, so there are lots of great places catering to an upscale, sophisticated crowd, but in a funky, hip setting.  South of Market is similar in terms of its urban/sophisticated vibe, but you're more likely to find big nightclubs and lots of industrial loft residences than you are to find boutique shopping.  Many of the city's big theme/concept restaurants (like Supperclub, AsiaSF, and Coco500) and hotels (the W San Francisco, the St. Regis) are in SoMa, due to this neighborhood's ability to accommodate larger spaces in converted warehouses or knocked-down blocks of auto repair shops and other industrial uses that is rapidly getting too expensive for the businesses that pulsed with the lifeblood of the area.

South of SoMa is South Beach and China Basin, which includes AT+T Park, home of the 2010 World Series Champions, the San Francisco Giants. The start and end of the local train line, CalTrain, is also based here (at 4th and King).  South Beach/ China Basin received a massive make-over in the early 2000s as the world-renowned UCSF medical center invested millions of dollars into a new campus there and developers built up dozens of mid- and high-rise mixed use buildings, featuring hip lofts, big box retailers, boutiques, restaurants and bars. A popular waterfront walk goes from AT&T park north on the Embarcadero, under the Bay Bridge (which connects San Francisco to the east bay), to the Ferry Building, across from Market Street (the main artery of the city), and onward toward Pier 39 and Fisherman's Wharf.

Two neighborhoods that are always overlooked in SF are the Sunset and Richmond districts on the western end of the city. They are residential in nature and usually considered an afterthought at best when lining up the sights to see in San Francesco. However these neighborhoods have more to offer than most people realize. First both of them ride along the western coast of the city- meaning easy access to Ocean Beach. Secondly attractions such as the SF Zoo and golden gate park are found in the western end of the city. Some of the best restaurants are located here- I’m not talking about the fancy high-class establishments but those really good family style ones. Unlike some of the more ethnically specific neighborhoods like China Town and the Mission- The Sunset and Richmond districts are melting pots- so you can find diversity in everything. 

Tip: a great way to experience the vitality and culture of San Francisco’s communities is to join them in celebration. Many communities hold annual street festivals from June through September – here are just a few: Union Street Art Fair – 1st weekend of June; Haight Street Fair – 2nd weekend of June; North Beach Festival – 3rd weekend of June; the Folsom Street Fair – 4th weekend of September (not for faint of heart or anyone traveling with small children, as people dressed in leather, chains and not much else roam the streets); Bay to Breakers- 3rd Sunday of May (again, not for faint of heart, as risque costumes, nudity and public drinking, however friendly and harmless, tend to dominate the scene more than actual competitive runners do.)

An excellent guide to all San Francisco neighborhoods can be found here

http://www.sfgate.com/neighborhoods/