The spot in the Mile-High City that's exactly 5,280 feet above sea level (at least for now).

Man-made geyser that rises to the exact height of the Gateway Arch.

Visit this playground of waterfalls, caves and sinkholes.

The world's longest known cave system.

This London pub hides a peculiar secret: a recreation of the rooms shared at 221b Baker Street by Sherlock Holmes and Dr. Watson.

A century-old tradition has culminated in a small but singular collection of feline effigies.

A series of abstract, silly sculptures represent the works of a great modern classical composer.

This life-size replica of the Statue of Liberty's flame is also a tribute to Princess Diana by default.

In the best of all possible worlds, everyone will get a chance to see this statue in which Voltaire's heart is interred.

This bridge was constructed from the rubble of the infamous Bastille.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

The comedy and tragedy of Oscar Wilde is preserved in a Dublin park, captured in a sculpture of colorful stone.

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

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

A majestic lion statue guards this Parisian botanical garden, and feeds on an unsettling item.

Paris' fabled purveyor of exotic taxidermy and natural history curios.

The celebrated eyesore created by starry-eyed sweethearts.

Several plaster noses are hidden in plain sight around London's Soho neighborhood.

The popularity of Sherlock Holmes led to the creation of his fictional address, turning the orderly London street numbers askew.

Kings Cross Station pays tribute to its role in Britain's best-selling book series.

Famously misunderstood wonder of the ancient world

The first archaeological site discovered by aerial photography.

Europe's largest prehistoric mound – burial site of a legendary king?

The largest stone circle in the world has ended up bringing up more questions than it has answered.