An impressive cavern through which a river flows under a mountain in the USA

Nature has given rise to spectacular places, some of them hidden deep inside the mountains.

The great cave of La Cuevona de Ribadesella, in Asturias, and its beautiful natural surroundings
A tour of the incredible Son Doong Grotto, the largest cavern in the world

Today we get to see a good example of these hidden gems: a river cavern that thePOVchannel showed in a video posted yesterday. The author doesn't provide any details about its location (I've tried to track down this site but couldn't find it). He only notes that it's in the United States, but comments: "Thermal Springs in the ceiling create bizarre cave formations, and calcifies the ruins of an old log flume in minerals."

The images are truly spectacular, especially those seen inside the cave. In the video, the author barely says anything, letting the murmur of the river take center stage:

You can see some screenshots from this video here. Here we see one of the cave entrances:

The interior of the cave. The intense green colour of the moss on the rock wall on the right, in one of the places where sunlight reaches, is striking.

The curious shapes seen inside the cave are the result of the combined action of water, lime and time.

A picture of the outside of the mountain. There appears to be an old, destroyed wooden bridge.