San Francisco (SF) is the cultural, commercial, and financial center of Northern California, USA. It is the second-most densely populated major city in the United States after New York City. It has a Mediterranean-type climate with consistent, moderate temperatures. It is a popular tourist destination it is known for its cool summers, steep rolling hills, fog, landmarks and eclectic mix of architecture including the Golden Gate Bridge, the former prison on Alcatraz Island and cable cars. San Francisco is also the headquarters of five major banking institutions and various other companies such as the Pacific Gas, Yelp, Pinterest, Electric Company, Twitter, Mozilla, Uber and Craigslist. San Francisco's coastal location and natural harbour have made it an important shipping center. San Francisco offers state-of-the-art health-care facilities. Tourism is one of the city's leading industries in San Francisco as it has natural beauty, mild weather, and cultural attractions.