California's spillway, known as the 'Glory Hole,' in action

The "Glory Hole" is the nickname for the spillway at the Monticello Dam, located in the Lake Berryessa reservoir in Northern California. It's a massive, circular drain used to release excess water from the reservoir when it overflows. The technical term for the Glory Hole is the "Morning Glory Spillway."

When the reservoir reaches full capacity due to heavy rainfall or snowmelt, water flows over the spillway and down the hole, creating a visually stunning vortex that drops the water into a vertical shaft. The sight is particularly dramatic, as the water spirals into a hole with a 72-foot diameter. The spillway only activates during rare instances of extremely high water levels.

When it's in action, it can be a breathtaking sight, especially when captured in photos or videos. However, the Glory Hole isn't just for show it serves a crucial purpose in flood control, helping to prevent dangerous water levels in the reservoir from reaching critical levels.