This sculpture by artist Fritz Keonig survived the 9/11 attacks and now stands as a monument to the victims.

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

Whisper secrets in a busy station only to be heard on the other side of this acoustic arch.

Manhattan’s Battery Park has a whimsical carousel full of spinning, glowing fish.

Richard III supposedly disposed of his nephews' bodies here in an effort to seal his claim to the throne.

The watery entrance for condemned prisoners heading to the Tower of London is still visible along the Thames.

An easily overlooked stretch of ornate window fronts and gaslight lamps that could be right from the pages of Dickens.

Eighty million natural history specimens call this gargantuan museum home.

A 300-year-old tea shop that brought tea to the English people, not to mention the Queen herself.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

A mysterious chasm in the heart of the ancient Roman Forum, the Lacus Curtius was once believed to be a gateway to hell.

The engineering wonder and pleasure dome of a much-maligned emperor still holds undiscovered secrets.

One of Catholicism's four major basilicas has a series of papal portraits that are said to predict the end of the world.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

This bronze boar's snout has been rubbed to a golden sheen by visitors seeking good fortune.

Over 50 exquisite hand-painted Renaissance maps decorate a Medici storage room.

The mummified relic of St. Antoninus.

In Florence's great Duomo, a 26 foot fresco honors a mercenary famous for attacking Florence.

Art and armour fill every inch of this rich kid's Italian villa.

A slightly creepy gallery of plaster cast models in the same museum as Michelangelo's David.

The remains of a community that was forced to move for a dam that never materialized still rot in this Pennsylvania park.

This stone tower marks a lookout point over the historic Washington Crossing, and maybe some buried treasure.

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

The first declared National Monument in the United States.