Straying radically from the ideal of the quiet museum – one filled with the archaic artifacts of yesteryear, each lighted softly and placed behind Plexiglas – the San Francisco Cable Car Museum is a place of restless activity, and for good reason. It's the hub of the city's cable car system – a clamoring dynamo of giant spinning sheaves that pull the cable cars up the cities famously steep streets.

Anyone who's ever wondered about the inner mechanics of San Francisco's cable cars can experience them firsthand here. Each streetcar is pulled along a huge continuous loop of cable, which is constantly turned by a giant spinning sheave. These enormous sheaves - wheels with grooves along their edges for holding cable - can be seen working away at the Cable Car Museum, always moving the huge loops of cable running under Hyde, Mason, California, and Powell streets.

Streetcars move by clamping onto the cable and being pulled forward. Car operators must quickly let go of the cable when taking certain turns or when one cable car crosses another, and then quickly clamp on again. The cables, sheaves, and cars must be kept in excellent condition to avoid runaway streetcars, of which there have been only a handful in the history of the city.

The Museum's mezzanine offers a subterranean glimpse beneath the city streets of the cables, sheaves, gears, and electric motors that run the system.