A herd of 150 bison live on California's Santa Catalina Island and are at the heart of an ongoing debate between environmental protection and economic expansion.

According to tradition, King Phillip II supervised construction of the seat of his empire from this seat carved into rock.

A futuristic climate change study is nestled deep within this public land.

This ancient fort overlooks the site of a disastrous retreat from the English Civil War.

These magnificent city walls rise from the barren sun-baked Spanish plains like something straight out of a fairytale.

The interior of this Serbian royal family's mausoleum is covered with exquisite mosaics.

Just your average Marie Antoinette–themed speakeasy in an abandoned 19th-century subway tunnel.

This water tower has been a staple of the Rochester skyline since 1931.

It was an experiment to prove that glacial boulders and rocks can be used in constructions and dwelling.

This medieval sanctuary's tree-framed door looks like a portal to a mythical realm.

Edison's cast-in-place concrete houses were a failure, but way ahead of their time.

This grassy, tree-lined hill shares a name with the much-loved novel that it inspired.

A tribute to the movie stars who fought to keep Beverly Hills separate from Los Angeles.

This abandoned subway station beneath the Waldorf-Astoria hotel is allegedly used to secretly transport presidents.

An unassuming secret door once led to a legendary watering hole.

Hidden in plain sight on a pair of Manhattan subway tunnels are a pair of public instruments that sing to each other.

During the holidays, a vintage subway train whisks New Yorkers back in time.

This 7,000-year-old megalithic wonder covered by a Franco-era reservoir emerges in times of drought.

This Aztec structure remained hidden until the demolition of a supermarket exposed the lost temple.

A neighborhood park in the city of Cáceres hides what some believe are revolutionary examples of Neanderthal cave art.

The Dead Sea Scrolls were discovered in the ruins of this ancient monastic community.

The ruins of a medieval castle that once belonged to one of the most powerful families in the Netherlands.

Double spiral staircases are not unheard of, but they are very rare.

Climb this overlooked gem's spiral staircase and you'll be rewarded with spectacular views of Glasgow.