Long attributed to a meteorite, this beautiful swimming hole is actually a naturally occurring sinkhole. Sinkholes are often the result of groundwater eating away at rocks like limestone and carbonate. Caverns form as the rocks dissolve, and eventually the ground above caves in, sometimes taking cars, houses, and even the occasional pizza place with it. In Northern Oman, just off the road between Dibab and Bimmah, there’s a particularly beautiful example of the natural phenomena. In an otherwise flat area, a sinkhole formed about a third of a mile from the sea, resulting in a turquoise mix of fresh and salt water.