How to Tour

I've been looking at a few different ways to tour the big cities like Madrid and Barcelona, with the few hours I have in each. The hop on hop off buses seem like a good idea but I'm not sure if there is a better way to do it. I found a company that rents out little go carts that you can drive throughout the city. They charge per hour, and have a gps built into them. They seem fun, but you need two people in it to rent it I think.

Go Car Rental