A closer look

Sometimes brilliant engineering just accepts defeat against the weather. The ancient Roman Pantheon features an unreinforced concrete dome that is structurally flawless, complete with a massive 27-foot open hole in the center called the oculus. Instead of trying to put a glass roof on it, they simply let the rain pour right inside onto the marble floor, where a cleverly sloped drainage system sweeps the water away. It's majestic, but highly inconvenient during a downpour.