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.

A journey begins with a single step, and for many, the road-trip of a lifetime started at this Chicago intersection.

The ruins of an Estonian prison are drowning in the quarry lake where the convicts were once forced to work.

This dizzying tower was built to better broadcast the 1980 Moscow Olympics.

A former imperial sea-fortress and Soviet prison.

This medieval Estonian tower provides access to a series of tunnels that have been home to soldiers, punks, and fine art.

Only a fragment of this 15th-century Dance of Death survives today.

"There's nothing there," and other lies the KGB told us.

One Portuguese poet described this cape, the westernmost point in mainland Europe, as "where the land ends and the sea begins."

Single runway interrupted by a busy road that cuts across its middle.

A labyrinth of ancient tunnels hidden below the city holds the ruins of 2,500 years of history.

Thousands of well-dressed mummies below a monastery.

A new sculpture calls attention to climate change in the centuries-old city it threatens.

Venice's island of the dead.

This massive subterranean fissure is known as the "underground Grand Canyon."

Now abandoned, the world's first torpedo factory is crumbling into the sea.

The walls of this medieval church are covered with perfectly preserved frescos, including a pristine example of the Dance of Death.

The Adriatic's most famous wind can be reliably experienced in the city's Marina.

During World War II, this rice mill became a Nazi concentration camp.

One of the tallest lighthouses in the world also serves as a monument to the fallen of World War I.

Two bronze wolves atop this large rock honor the "Wolves of Tuscany" brigade of World War I.

This Roman monument is surrounded by more recent construction, offering a stark contrast between ancient architecture and the modern urban landscape.

This historic floating crane became an unlikely symbol of the port of Trieste.