The second-most densely populated major city in the United States after New York City, San Francisco is a stunning 49-squar-mile peninsula along the Northern California coast. As a progressive, coastal town, San Francisco is divided into several precincts, from urban, posh and artsy to rugged and outdoorsy. From the lively Chinatown, and the spectacular North Beach to the calm Presidio, the city is home to a myriad of attractions. Here are some of the important areas of San Francisco, that you must know about, before visiting the city.