Famous YouTuber Explores the Underwater Gold Rush Town in Folsom Lake

A lost Gold Rush city buried beneath Folsom Lake is getting fresh attention after a new deep-dive exploration from YouTube creator Mark Rober. Armed with sonar technology and even a two-person submarine, Rober set out to locate the remains of a once-bustling mining town submerged when the Folsom Dam was completed in 1955.

The valley beneath the lake once held a thriving community of a few thousand residents during the 1848 Gold Rush. Old hotels, saloons and wagon routes disappeared under more than a billion tons of water, leaving only stories and historic records behind. Rober wanted to know whether any traces of that forgotten town still exist on the lakebed.

Joining forces with geohydrologist Dr. Todd Kincaid, the team scanned roughly 30,000 acres using a torpedo-shaped device that fires sound waves downward and reads the returning echoes. The technique works much like echolocation, allowing researchers to map shapes and structures—even through layers of sediment where cameras cannot reach.

The mission wasn’t smooth. Equipment failures, murky conditions and false readings slowed their progress. But persistence paid off, and the sonar ultimately revealed several surprising features on the lake floor, including structures believed to be remnants of the long-lost settlement.

Rober’s full expedition is documented in the video below. For anyone fascinated by hidden history in Northern California, this underwater journey into Folsom Lake is a must-watch.