Giant Old Water
Gođafoss, or "Waterfall of the Gods", in Northern Iceland, near Mývatn. You can walk right up to the volcanic-rocky surrounding lip. Apparently about 1000 years ago, a 'law-speaker' decided Iceland would be a Christian nation, and threw all the carvings of Norse gods into the falls.
The actual sound is much louder, more full, and inescapable up-close, but walking just a bit away, it seems to fade almost to nonexistence.