The commemorative stone column conceals a secret laboratory.

Six ravens are kept captive (but well-fed) at the Tower of London to prevent the fall of the Crown.

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

This pump on the bad side of Victorian London betrayed a horrifying revelation about the water supply.

Mary Kelly was last seen here before she was murdered by Jack the Ripper.

The world’s largest truck stop includes a barber shop, chiropractor, and a huge museum with antique trucks.

An enormous park-like oasis, full of famous Chicagoans' graves.

A haunting statue called "Eternal Silence" has quite the reputation among visitors with active imaginations.

This historic house museum that celebrates one of the world's most influential social reformers is also one of the most haunted locations in Chicago.

This whimsical Oz-themed park had a wonderful impact on the surrounding neighborhood.

Chicago's Navy Pier on Lake Michigan was a training hub for aircraft carrier pilots during WWII.

What's left of the ruins of the 1893 Columbian Exhibition, or World's Fair, also known as the White City.

This memorial plaque remembers a strangely shallow maritime disaster known as "Chicago's Titanic."

A spectacular remnant of an Adler and Sullivan masterpiece that was destroyed in 1972.

This alley in downtown Chicago held the bodies of over 600 people after the fateful Iroquois Theatre fire.

Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.

The last masonry skyscraper ever built reveals a transitional moment in architectural history.

A 400-foot-tall tall map of Chicago makes this once-ignored building stand out.

Fragments of architectural wonders from around the globe are embedded in the newspaper building's walls.

Every equinox this Maya pyramid puts on a spooky ancient light show.

Clap your hands at the base of the pyramid, and the song of a sacred Mayan bird will echo through the air.

A magical sinkhole on the Yucatán Peninsula is adorned with mini waterfalls and hanging vines.

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

A fitting attraction for the corn capital of the world.