Columbus Tower, also known as the Sentinel Building, is a mixed-use building in San Francisco, California, completed in 1907. The distinctive copper-green Flatiron style structure is bounded by Columbus Avenue, Kearny Street and Jackson Street, straddling the North Beach, Chinatown, and Financial districts of the city. Much of the building is occupied by film studio American Zoetrope, and the ground floor houses a cafe named after the company. The Sentinel Building is San Francisco Designated Landmark No. 33. [Wikipedia]