THE MORNING GLORY SPILLWAY, AKA "THE GLORY HOLE".

The Monticello Dam holds back Lake Berryessa in Napa County, California, USA. The morning glory spillway associated with the dam is the largest in the world; it is a funnel-shaped outlet that allows water to bypass the Monticello Dam when it reaches capacity (1370 m³/s).

The Glory Hole is located about 61m from the dam; the distance from the funnel to the exit point - which is situated in the south side of the canyon - is about 213m. The outside diameter is 22m, slowly narrowing to 8.5m at the exit.

Water spills over the lip of the Glory Hole when the lake reaches 1,976,037,908 cubic metres (1,602,000 acre-feet). The spillway is designed to handle a maximum of 1,370,319 litres of water per second (362,000 gallons of water per second); this happens when the lake level rises to 4.7 metres (15.5 feet) above the level of the funnel.

Swimming near the glory hole is prohibited. Unfortunately in 1997 a UC Davis graduate student was pulled into the glory hole while swimming and drowned. Skateboarders and bikers sometimes use the spillway's horizontal exit as a half-pipe during the drier months, when the water levels are well below the rim of the glory hole.