A mass grave for victims of an airline disaster that led to much-needed safety improvements for commercial flights.

An abandoned train station in Munich constructed for the 1972 Olympic games.

A medieval church built into an ancient cave.

An enormous, inside-out glass globe built in 1935.

On the Spree bank, discover one of the last reminders of a symbolic wall that divided, and was torn down by the people.

An abandoned NSA listening post on Berlin's "Devil's Mountain."

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

In memory of the 110 victims of ValuJet Flight 592 that crashed in the Everglades.

An abandoned saucer-shaped monument in the Bulgarian mountains.

The shattered remains of the world's once tallest structure.

This futuristic German television spire is actually the world's largest digital clock.

A model memorial to the original Odin Tower, the second highest tower in Europe before it was sabotaged by Danish Nazis.

Once standing on solid ground, this slender beacon is a victim of the very shoreline it was charged with announcing.

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

The only microgravity tower in Europe can produce nine seconds of weightlessness.

A half-size replica of the World Trade Center towers above Tulsa.

This striking observation tower shaped like a spinnaker sail is the newest icon in historic Portsmouth.

This line of 12 tower mills described in the story of Don Quixote is among the most iconic landscapes in Spain.

This abandoned viewing platform has become a monument to unnecessary government spending.

Kuwait City's uniquely designed water towers look straight out of a retro sci-fi cityscape.

This 135-year-old weather station studied the effects of the climate on human health.

Former bridge turned into an observation tower.

A monument to the thousands of Canadian soldiers who died capturing the French ridge during World War I.

This stone memorial commemorates a group of French patriots slain by French fascists.