California: There is a mysterious hole in Lake Berryessa in California. It is not a supernatural whirlpool, a demon's mouth or a portal into hell or a fourth dimension. The creepy thing probably won't suck you into it either.

It is just a really big drain called a spillway. And once you see it full of spiralling water, it is hard to take your eyes off it.

For the first time in a decade, January and February have brought so much rain that the lake in the Napa Valley area north of San Francisco has maxed out its water capacity. To prevent flooding, this 22-metre-wide concrete funnel is sucking down the excess. Hundreds of locals have gathered to watch the show and take photos and videos since it started on Friday. And the show isn't over. More storms are expected toward the end of the week, and the flow may continue for up to two weeks.

"I went up there the other day and there were about 15 drones flying around and people taking videos," said Kevin King, an operations manager at the Solano Irrigation District, which oversees the day-to-day activities at the dam. "It's really dramatic to watch."