Abyss Pool is called so because of how deep this pool looks. I tried to capture that in the photo and I hope it sinks in. No pun intended... okay, maybe a little bit.
You can find this hot spring in the West Thumb area. There is also another pool close to this one called Black pool as it looked so dark. Hopefully, I didn't mix the two up because I was simultaneously taking pictures left and right that I might have messed up the name. n_n;
This was taken at Yellowstone National Park in Wyoming, USA in 2008.