San Francisco's Lombard Street is the most crooked street in the world. When it was designed and built in the 1920s, its purpose was to provide some relief for busy traffic. Now, however, it has become one of the most attractive streets in San Francisco. Lombard Street is actually quite long, but in the short block between Hyde Street and Leavenworth Street, there are eight hairpin turns. Because of the 40-degree slope and its "Z"-shaped curves, vehicles can only travel down it in a one-way direction...