Providing air conditioning to an entire city is no easy task, especially if that city is located in central Mongolia. Ulan Bator, the Monglian capitol, is planning on trying out an ambitious geoengineering project: they want to create their own urban glacier on top of a river, and rely on it to keep cool all summer long.
Making a giant block of ice out of a river isn't really that hard, as long as you can get started when it's still freezing out. Once the river has frozen over on its own, you simply drill some holes through the ice down to the running water, and let the river flood up over the ice. The fresh water freezes overnight, you drill another hole, and repeat the process until you get a big block of ice made up of lots of little frozen layers, up to twenty feet thick (or more).
A river of ice several tens of feet thick (let's just go ahead and call it a glacier) can last for months, even during the summer, and the idea is that as the ice slowly melts it will help nudge urban temperatures down and save on energy costs while also providing a steady supply of fresh water for drinking and irrigation. Nobody's quite sure whether the $725,000 investment is going to ultimately pay off, but if it does, northern cities around the world could potentially benefit from this technique.