The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

An acoustic anomaly with a mysterious cause sits in the heart of Tulsa.

A modernist landscape of water and sci-fi concrete.

This cemetery has graves dating back to the 17th century, including the city's oldest carved tombstone and an ominous cryptogram.

This knobby, drooping New Orleans oak is a favorite place both for climbing and for meeting giraffes.

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

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

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

This New Orleans tree is filled with hidden chimes that produce a carefully tuned melody.

The ancient dwellings of the Puebloans, located in the cliffs of majestic mesas.

A theme park that suffered massive flooding during Katrina was abandoned, and now proves irresistible to trespassing explorers.

Despite the name, this 16th-century structure in Galway wasn't built by the Spanish.

The ruins of a sixth-century monastery sit on the banks of the River Shannon.

The ruins of a monastery that dates to the 7th century.

Dublin's most modern, visually spectacular bridge is modeled after Ireland's national emblem.

The oldest licensed distillery in Ireland.

The modern birthplace of Irish freedom.

A stunning Victorian abbey and walled garden on a lakefront.

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

A bronze statue of a low three-legged seat commemorates a piece of furniture that started a riot.

A never-finished memorial to the heroes of the Napoleonic War has become "Scotland's Folly."

This painting of a beloved dog will be on display at the Scottish National Gallery at long as the museum exists.

The Scottish Reformation leader's grave was paved over and is now a parking lot.

Edinburgh's oldest statue hides within a parking lot behind the city's iconic cathedral.