Geology

This stunning natural double arch, the largest in the Alps, went undiscovered until 2005.

An unusually designed bridge from the 1920s was built to withstand the tides and winds of Maine.

A perfectly circular lake is formed by the crater of an ancient underwater volcano.

This hollowed salt dome is the largest oil storage facility in the world, hoarding 250 million barrels of crude oil.

A strange rock formation with numerous legends trying to explain it.

A natural rock formation believed to be a cure-all.

The discovery of this Neolithic settlement, which contained a Stone Age "cathedral," threw archaeologists for a loop.

Iceland's largest geothermal mud pool is a little bit haunted and a little bit dangerous.

Constructed thousands of years ago, these stone circles offer incredible insight into the lives of the people who built them.

Unusual hexagonal rocks formed by cooling lava named for their resemblance to traditional Japanese tatami mats.

A red sandstone freestanding monolith rises out of the sea in northern Scotland.

A sea cave with a waterfall and Viking past

A 70-foot-deep ice cave formed by lava from Mt. Fuji on the edge of Japan's "Suicide Forest."