Monticello dam (California)

The big man-made hole is in Northern California, the USA. But it not simply hole. Drain opening in the tank of a dam of Montichello — the biggest spillway in the world! It built about 55 years ago. This funneled exit is simply irreplaceable here. He allows to dump quickly surplus of water from the tank when its level exceeds admissible norm. Such protective valve. Waters merges with an improbable speed capable to bear all on the way, it dread to think that will be if the person gets up opposite to a pipe from which the thick stream of water beats out. But most it is terrible if somebody fails in this pipe, or will climb specially having counted it as a waterslide...

Visually the funnel looks, as a huge concrete pipe. It is capable to pass through herself in a second already 1370 CBM of water! Depth of a such hole — about 21 m. From top to bottom it has the cone form which diameter at top reaches nearly 22 m, and from top to bottom is narrowed to 9 m and leaves on the other side of a dam, removing at reservoir overflow surplus of water. Distance from a pipe to point of an exit which is located a little to the south, about 700 foots (about 200 m).