A windcatcher is a device used to help cool a house in warm weather. They are most commonly seen in Middle Eastern countries, and are very simple to use.
Essentially, the windcatcher is a large box-like structure that is placed on the roof. The windcatcher has openings on both the top and the bottom. When the wind blows, it goes through one of the opening and into the windcatcher. Hot air rises, so the hot air from the house rises and goes out through the opening on the top. This leaves the house feeling much cooler.