The Lake Berryessa spillway near San Fransisco - The largest spillway in the world. And people think I am crazy for having a water phobia. My mind has always imagined one of these in every large body of water I have ever been in.
Glory holes are used for dam's to drain excess water during dry seasons. This is the largest one of them all in the world, it is located in Lake Berryessa. It is used very rarely, but it is quite the sight to see it being put to use.