Collapsed adit, Mae Lundy mine

This was a gold mine high in the Sierra Nevada of California, just east of Yosemite National Park. The mineralization was in a metamorphic roof pendant. Activity began sometime before WW I IIRC, and was shut down in 1942 as per President Roosevelt's executive order. There was an abortive attempt to reopen it in the 1970s, during the last precious-metal boom, but by that time environmental considerations had much more weight. It's now in a wilderness area, a good 3 miles in and 1500' up. Vehicle access was shut off back in the 70s.