A few days ago I posted a photo I shot at Folsom Lake showing a high curved rock wall. I took my initial pictures from a distance and didn’t have a chance to explore the wall more closely — but when I got home and started looking at the area on Google maps, something odd caught my attention.

Google Maps screenshot

The screenshot shows the lake at a higher water level, but the curved structure can be seen, cutting across a small inlet. I was determined to examine that spot when I returned to the lake last Thursday and to hopefully learn more about this stone wall.

Southern approach

I was hiking from south to north, following the path of the former North Fork Ditch which is now mainly used — when it is out of the water — by hikers, mountain bikers, and equestrians. Although it’s easy enough to walk across the top of the wall structure, the main trail actually loops around behind it; you can easily see this on the screenshot above.

I’ve consulted to Kevin Knauss’ book Hidden History: Beneath Folsom Lake as well as his blog (specifically this post, which includes a short video) for more information about this unusual feature of the Folsom Lake landscape. On his blog he refers to the structure as a “viaduct,” although in the book he more properly calls it an aqueduct, since its use was more likely related to water rather than transportation.

Looking north; note the gully on the “inland” (left) side of the wall