Currently the seventh largest man-made lake in California is most known for its 'Glory Hole', as it is locally known, which can be observed right next to the 93 m high Monticello Dam. This awe-inspiring 22 meters wide and 75 meters long hole is actually the Lake Berryessa spillway in Napa County. When the lake fills up, excess water pours down the pipe and out the base of the dam. At the lake's peak level (4.7 m above the level of the funnel) the spillway can drain approximately 1,370 m3/s. 

The amazing drone footage below will show you how amazing it is to witness the sheer power of the spillway from up close. If you watch it carefully, you'll notice how the drone was almost lost to the deep hole at one moment.

Such an amazing, exhilarating watch, do give it a go!