Inexplicably located in the absolute middle of the desert, near a desolate stretch of highway between Los Angeles and Las Vegas-- miles away from even the smallest town-- Lake Dolores Water Park was operated off and on for about forty years, until the early 2000's when it closed for good.
How it came to exist seems to be a bit debated, but the origin story I'm fondest of is that it was a piece of personal property, developed by the land-owner initially as a water attraction for his wife, and only later on was the decision made to open it to the public.
Here's an advertisement for the park from the 1980's:
Even today, there's still a lot of the park that remains including a lazy river, some water slides, a lot of structures, and the dusty indent of what was once a "lake" large enough to ride jet skis on.
Climb the steps to the highest slide platforms for a great view. Wander the buildings and explore the empty lockers, the offices, and the maintenance rooms. Climb the empty water tower just outside the fence if you dare (we did not).
Next time you're going to Vegas on the 15, check it out. It's a fascinating relic, made all the more interesting by the magnitude of it's hubris -- a waterpark in the middle of the desert. I hope they leave the park there forever, because we're not likely to see anyone attempt something like this again soon.