Aqueducts have dramatically changed this old lake, now home to tufa towers and its very own species of tiny brine shrimp.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

A Norwegian-born sculptor created these soaring guardian angels at the entrance to Hoover Dam.

Experience a charming 1930s version of "infotainment."

A sharp bend in a dramatic river canyon cut through red rocks.

A roaring, awe-inspiring double cascade of icy water flows through woodland Oregon like something out of a Tolkien novel.

The longest continuous lava tube in the continental U.S. offers 2.5 miles of dark explorations for the adventurous.

This extravagant Art Nouveau rest stop features a million-dollar view of the Columbia River.

On the Spree bank, discover one of the last reminders of a symbolic wall that divided, and was torn down by the people.

A formerly glacier-tipped volcano that inspired none other than Jules Verne.

This mountain fissure hides a secret path to a secluded mossy grotto within the rock itself.

Iceland's largest lagoon is home to stunning multi-colored icebergs.

Three columns of volcanic rock shoot out of the ocean.

This wrecked airplane has been sitting on a black sand beach since the 1970s.

Twisted girders are all that remain of an Icelandic bridge that was wiped out by a combination of volcanic heat and glacial floods.

This eye-popping Icelandic crater lake is surrounded by red volcanic rock.

A sulfuric martian landscape that looks far better than it smells.

These ominous lava formations were said to be an entrance to the netherworld so of course they inspired a famous metal band.

This hobbit-y little hot spring may be the oldest spring used by humans in all of Iceland.

This elegant arc of a waterfall marks a religious turning point.

Rising from the sea like a stone monster.

Partially collapsed lava tube and cave system complete with concert hall, underground pond, and unique albino crabs.

Visit a surreal landscape so otherworldly NASA actually used it to train the Apollo 17 crew.

This mountaintop observatory is home to one of the world's largest reflective telescopes.