I was out on a hike with the family and found the little building in the picture. Obviously I had to check it out. Found two tunnels, the first one appeared to be collapsed maybe 10-15 feet in and the other went deeper than my headlamp. Both appear to have about 2.5’ of water in them. I returned with a brighter light a few days later and discovered the “cave-in” was actually cement, looks like it was poured from the opposite side. The other tunnel just kept going.

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No surprise I want to figure out what this was, cement anchored stones line the walls as far back as I can see and there’s vertical supports too. Need to talk to a buddy about borrowing a dry suit (water is COLD, probs in the 30s). There’s no discernible current and water levels hasn’t changed between my two visits. The bottle floating in the foreground was there both visits as well.

Does anyone have advice for this kind of exploration? I’ve got some very basic subterranean training from the Army back when we were worried about going into Korea, but the rule of thumb for water is that if don’t want to cross neither does the bad guy. Obviously I’ve got a buddy to standby the entrance with a tether. Any other advice would be appreciated!!

looks pretty cool! i would get some knee high wadders and go for it. watch your head!

What a cool find! Definitely leave an update if you go further in

Are there any roads on the hill above? We've got a couple of identical tunnels here in the hills of LA, and they're drainage tunnels for the roads on the hillsides above. I know, not very magical, but something to check.