The former hotel where Tesla invented the radio.

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

Unrepaired walls from a 1920 anarchist bomb attack.

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

Avoid gangster interaction while window-shopping.

A large grotto built in the 16th century amidst Florence's famous Boboli gardens.

This landmark cemetery in Boston was created more than 300 years ago.

2300-year-old Roman road connecting the empire.

Hundreds of prehistoric stones, arranged in perfect lines in a French field.

This mosaic dedicated to John Lennon was tended for years by a Beatles super-fan.

Breathtaking and huge 430 year old maps of Italy.

The 340-year-old house that inspired the classic Nathaniel Hawthorne novel.

The only structure left with direct ties to the Salem witchcraft trials of 1692.

The tomb of Increase Mather and his son Cotton, influential colonial ministers obsessed with the occult.

Island where motor vehicles are banned -- home to the only carless highway in the United States.

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

At Chicago's revered Field Museum, visitors are invited to learn about and literally explore DNA.

No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.

Macabre astrological automaton clock dating to the late 1400s.

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

"the sweltering inhabitants of Charleston and New Orleans, of Madras and Bombay and Calcutta, drink at my well . . . The pure Walden water is mingled with the sacred water of the Ganges."

One part local history, 99 parts gruesome haunted house.

This blowhole is supposedly caused by a trapped monster.

A prehistoric landscape hidden in the cliffs of Maha'ulepu.