Natalia said, "¿Why don't we make watia?" an Easter tradition. So we did.
First you make a dome of dirt clods, usually in the field where you JUST harvested root crops--potatoes or oca. A strong stone door is useful.
Then you build a fire and feed it until the dirt clods start to glow red hot. Next you rake out most of the ashes and coals and throw in a handful of potatoes. Knock in the dirtclods at the top of the dome and break them up. The soil is very sandy, so easy to break.
The kids made their own small watia and added fresh corn in the husk when it was ready.
After an hour or so, come back and dig it all up. Some potatoes are a bit burned or crispy like potato chips, but mostly the food is perfectly cooked and wonderful. Brush off the sand (Hey! it's sterile!), wrap it in an uncuña (handwoven food-carrying cloth) and gather the family around. We dipped ours in avocado-onion-tomato, fresh piquante salsa, and the traditional salty green clay. Sometimes they make lakeweed (like seaweed) cooked in milk.
When we roast the same vegetables in the solar oven, using no fuel at all, people always say, "Oh, it's just like watia!"