Gear

One of my recommendations when visiting San Francisco is to go to the trolley museum. The trolley system in San Francisco is a fascinating bit of old engineering. The trolley cars themselves do not have motors. Instead, there are cables that run under the street that are pulled from a central location. The cars latch onto these cables and get pulled along. I'm sure no one would build one of these now since it isn't particularly fast and maintenance is hard, but they sure are nice when you are facing climbing the next hill.