This structure, built more than 60 years ago to manage devastating seasonal floods, is known to attract a rare species of freshwater dolphin.

On a remote island, legend has it that a fiddler and his wife were turned to stone.

Possibly the oldest of Britain's ancient henges is also one of its most stark.

The 5,000-year-old megalith is believed to be Scotland's tallest standing stone.

The true age of this ancient stone circle is unknown, but its stunning vista isn't in question.

A trio of giant megalithic stones in the middle of a golf course.

The mysterious megaliths have enchanted and intrigued visitors for thousands of years.

A Spanish-style estate that has traded black ties for rock concerts.

All that remains of the fishing-vessel-turned-warship is its weathered hull.

This memorial honors five journalists who were killed in a mass shooting in 2018, and affirms the importance of the first amendment.

Perhaps the most spectacular grotto along the Algarve coastline.

This teeny-tiny park built by a San Francisco man in 1962 is mostly stairs.

Hiding in plane sight.

This twice-relocated "Usonian" home is among the smallest built by master architect Frank Lloyd Wright.

Slaughterhouse Five opens its dank doors to fans of Kurt Vonnegut.

Four steel monoliths stand in the Qatari desert, in a breathtaking work of large-scale art by Richard Serra.

According to local history, this cast-iron canine was nearly melted down for bullets during the Civil War.

A massive, gleaming sea turtle with a rider atop its shell looks out over the horizon.

An impressive bridge over a ravine also served as an aqueduct.

This quaint Italian town keeps losing ground as the sides of its plateau slowly erode.

Thomas Jefferson's estate is home to hundreds of varieties of historic fruits and vegetables.

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

This memorial commemorating fallen Swiss Guards of the French Revolution has been called the saddest stone in the world.

Rippling sand dunes frozen in the Arizona rock.