The Sinks of the Po-Po Aggie *
At Sinks Canyon State Park outside Lander, a major river just disappears. The Middle Fork of the Popo Agie (pronounced Po-Po-zsha, meaning Tall Grass River in the Crow language) rushes out of Wyoming's largest mountain range, the Wind River Mountains, and into Sinks Canyon. It flows merrily along for quite some time until it suddenly turns into a large cave and, as the name of the park and canyon suggest, sinks underground. It isn't until ¼ of a mile later that the river reemerges at a large, calm pool called "the Rise."
For a long time, no one was even sure the water at the Rise was the same water that disappeared into the Sink, but then scientists did dye tests and proved the two were one and the same. Tests also revealed more water emerges at the Rise than goes in at the Sink. No one knows where the water goes for the two hours it takes to get from the Sink to the Rise though … but that's just fine: curiosities and oddities are even more curious and odd when they can't be fully explained.
* If you saw the film, that's what Jeremiah Johnson called it.