Heralded as the world's first theater, these ruins are often overlooked as they reside in the shadows of the Acropolis.

Two stone columns flank the grand Venice square, but there were supposed to be three.

The stoic structure boasts a whimsical set of stained glass art commemorating Lewis Carroll.

Famously misunderstood wonder of the ancient world

The perfectly preserved underground rooms where Churchill plotted the war against Germany.

The commemorative stone column conceals a secret laboratory.

Scattered throughout London are ancient remnants of the city's former bounding wall.

A memorial for public executions that dates back to the 14th century.

One of the few standing Roman lighthouses and a labyrinth of tunnels are a couple of the secrets at this historic castle.

The last holdout of a pre-Civil War rebel who took the matter of slavery into his own hands.

There’s a special club house at the top for the bell ringers.

The sci-fi villain is a little-known inhabitant of the U.S. capital's largest cathedral.

Decades before the scandal, this staircase on the river was a literal "water gate."

This massive swimming pool is the high tech home to the human-powered submarine races.

The phrase "the shot heard around the world" was coined after a skirmish at this bridge.

This small section of the Sleepy Hollow Cemetery is rotten with famous authors' graves.

"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."

Louise Bourgeois' 30-foot-tall steel spider sculpture.

A tradition unlike any other, this marks the site of the annual Groundhog's Day tradition.

Once the "Eighth Wonder of the World," this iron railroad bridge was decimated by a tornado.

This extraordinary model train layout covers over 1,700 square feet, with multiple trains running simultaneously.

This vintage short line in Amish country runs passenger steam train excursions and still hauls freight.

A eight-foot-tall statue resides in the heart of Pennsylvania anthracite coal country.

The most gigantic, swoony, intimidating trio of fingers in all of antiquity.