This is the world famous Lombard Street in San Francisco. Known as “the crookedest (most winding) street in the United States”, Lombard street was re-created in Grand Theft Auto: San Andreas as “Windy Windy Windy Windy Street”. Its ridiculous switchback design was instituted 1922 in order to reduce the hill’s natural 27° slope, which was too steep for most vehicles. There’s some good ground-level shots at Wikipedia. Thanks to James Boorman-Padgett and Nathaniel Hansen.