So I had a feeling there was a big flood system under a nearby road to my place and had a itch to go walking so i scratched it ..lol and here is the result .

1. This is the entry to big round ones going into a good size box then into a long LONG stretch of square concrete
Couple hundred feet in you start to see these nice formations .

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on the way back out saw this dont know how i missed it . . seems like they tried to block it up but in time mother natures gonna win
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This trip I went all the way till the square pipe split into two smaller ones . I turned back at that point i was ready for bed . But will definately check em out next chance . .