At an altitude of 12,500 feet, Lake Titicaca is the highest navigable lake in the world. This means that you can sail on it. Work on it. Or even build floating islands on it, where you live with your family and sell over-priced souvenirs.
I realize that sounds cynical. But when your floating-island host makes canned in which he refers to his boat-made-of-reeds as a Volkswagon, and then charges you 15 Soles for a boat ride, and said ride takes you right past his motorboat which he didn't realize you'd see...
Still, it was a worthwhile trip, in which we learned about other cultures and the power of modern commerce.
After our visit to the floating island, we sailed for three more hours to a second island, called Amantani, where we stayed the night with a local family. We had electricity, but not much more: no running water (never mind hot water), no flushable toilet (merely a bowl that you poured water in), mattresses made of straw.
And yet it was once of the most magical nights of our trip - thanks to a massive thunderstorm that struck around 9pm, knocking out all electricity on the island and allowing the six of us to huddle together as a family beneath the pitter-patter of the rain on the tin roof overhead.