at first I wasted time on the negligee clue. the eventual name of Lake Peigneur was forgotten by me and I do not know French, and especially the very obscure french word
: a woman's loose negligee or dressing gown

Most important was Wagga's clue that the lake was no longer a fresh water lake. I first imagined the lake was meriometic. Nope.
Then I considered maybe it was a polder.. Nope.

What's left - it went dry? How could a lake drain, and have anything to do with an unusually-located "waterfall"? Could it drain straight down? But it did not look like a lake sitting in a crater. What's left? This led me back to how does a lake drain weirdly in France, French colony... no. How about a state? Ta-da, must be Na'leans. The overlooked salt mine clue resurrected itself at this point.

The clues in the pictures are all there. The Wagga tips are all there (I grudgingly acknowledge!) Just have to recognize them. Thanks