Not to be missed, The Maras Salt Ponds, Peru
I think people go to Peru because there are things in Peru that you cannot find anywhere else on Earth. The Maras Salt Ponds is one such place. They were original started by the Inca's and continue to be used, and expanded, today. What is most fascinating is that they are operated in the fashion that they have always been operated and that manual labour is still used to tend them.
The salt ponds consist of thousands of constructed ponds that are designed to hold roughly the same volumes of brine.
Here is how they work: All of the ponds are fed by a single, natural spring of hot briny water. The water from the spring is channelled through a single channel, initially. The channel can be seen in the photo below.
This chanel is used to fill all of the ponds below by gravity. Once a set of ponds are full, the channel is redirected to fill another set of ponds. The filled ponds are then left to evaporate.
Given enough time, the water evaporates and a more or less pure salt is left. The salt is then removed by hand shovelling it into bags. The bags are than carried by foot back up to the top of the pools near the source water. The salt is then further processed to a point where it can be sold.
It is an interesting ancient process that has changed little over the years. It is unique to witness and provides ample opportunity for some beautiful photos. You can access the site from Cusco and incorporate it into a tour of all kinds of sites along the Sacred Valley of the Incas.