This was an interesting thing to see in La Paz. It is about 30-40mins by bus from San Francisco and cheap entry. (It is much more for tourists than it is for locals, I'm guessing this is how they make their money, but it's still cheap!). You can book a tour around it but I didn't bother as I prefer to explore on my own - I'm not sure how beneficial a tour is. There are 2 ways around, a short or long version, and I took the long one. This could easily be done in less than an hour, but I took my time and snapped millions of pictures along the way. It is beautiful and fascinating to see and worth going to for a morning/afternoon.