This frequently-photographed waterfall takes only a short hike to visit.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

Macabre astrological automaton clock dating to the late 1400s.

This naturally-sourced hot spring is now home to a clothing-optional resort.

A breathtaking array of ancient Pueblo structures and artifacts counterintuitively preserved by neglect.

A 30-acre garden inspired by the principles of modern physics.

The intricate stonework of Machu Picchu serves as a testament to Incan engineers.

A one-of-a-kind collection of a unique medium.

At this Denver landmark, the meals are compulsory, the sopapillas are complimentary, and the insanity is everywhere.

Ruined 11th century abbey built by King David I in Edinburgh, Scotland.

The beautiful baroque library of the Hapsburg empire.

Where beautiful signs live on forever.

Seemingly grown on some other world, these New Mexico rock formations look like a disused science fiction set.

The first declared National Monument in the United States.

The most iconic structure in Scotland has been home to bishops, colonels, and Sean Connery characters.

This abandoned amusement park was built on a site with a dark history.

A Jenga-style cylindrical tower of books that appears to go on forever.

The gorgeous library at Trinity College is home to remarkable treasures of Irish identity.

The unique waterfall in Iceland's south features a backdrop of geometric black lava columns.

This 1,300 year old monastery built atop a single rock was once only accessible depending on the whims of the tide.

This 1920s Dutch barge is now a floating bookstore.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

Paris' linguistic guide to the international language of, yes, love.