Lombard Street is known for being the crookedest street in the world. I'm not trying to burst anyone's bubble but, in fact it's not even the crookedest street in San Francisco. Vermont Street between 20th and 22nd street is more crooked. But Lombard may be the prettiest crooked street in the world.
Lombard Street runs from the Presidio all the way to the Embarcadero. The famous crooked part is a 27% grade on Russian Hill with 8 switchbacks between Hyde Street and Leavenworth Street. This curvy part of Lombard is paved with brick and surrounded by beautiful landscaping and the 5 mph stretch of road takes you past some expensive homes.