Napa, California: Portal to Hell: Monticello Dam Drain

World's Largest Spillway Drain - spanning 28 feet at the bottom -- is best seen when Lake Berryessa's Monticello dam is at capacity and excess water goes down the concrete Glory Hole.

Address:: Hwy 128, Napa, CA
Directions:: SE reach of Lake Berryessa, Hwy 128 and Monticello Dam, parking near dam.
Hours:: Visitor Center Sa-Su 10-4 Local health policies may affect hours and access.
RA Rates:: Worth a Detour

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Visitor Tips and News About Portal to Hell: Monticello Dam Drain

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Glory Hole.

Portal to Hell: Monticello Dam Drain

March 2017, the Lake Berryessa level was its highest in years, and the Glory Hole was flowing.

[Thomas Jones, 01/21/2022]

Glory Hole.

Portal to Hell: Monticello Dam Drain

Full lake and glory hole.

[Shawn Vandergriff, 04/02/2020]

Nice view from Spring 2019, after a drought-smashing season of rainfall replenished California water repositories.

The Glory Hole, March 2017.

Glory Hole - Monticello Dam Drain

Here she is, finally getting to do what glory holes do!

[Jolene, 03/15/2017]

California's early 2017 drought-smashing rainfall is the culprit, restoring the this infrastructure attraction to full dam drain awesomeness. At least for a little while....

Glory Hole.

Glory Hole - Monticello Dam Drain

As we all know, California is in a drought, so the only view we got in May 2015 was the look of it when water is very low. Still an impressive spectacle with sparkling lake, surrounding dam and hills. Hope to see water overflowing into it someday soon.

Do note your view is through a chain link fence, and we did not see a visitor center nearby......worth a stop!

[Jolene, 05/04/2015]

The World's Largest Spillway Drain has been underemployed for several years. If the water ever returns, the Glory Hole will do its thing.