Once a meeting point for great thinkers, and the midpoint of the country.

The old observatory in Copenhagen has a spiral corridor used as a racetrack.

Danish tourist destination well known for open stalls where vendors sell marijuana on the street.

Climb to the top of its spiral spire for spectacular views of Copenhagen.

This bridge's unique architecture honors nautical heritage and encourages self-awareness.

Copenhagen's "other" little mermaid marks the historic location of past sea maid sightings.

The American Revolution was galvanized into serious action due to the tragic clash with British soldiers that occurred at this location.

Fragments of a massive unfinished sculpture sit near the main quad of the University of Illinois.

The oldest experimental corn field in America is still creating better ways to grow crops.

This slowly crumbling mansion was home to one of East Africa's richest and most powerful slave traders.

This sacred, circular cave is lined with pools so clear and still that it's hard to tell where the water begins.

This monument is a stark reminder of the horrors of the Zanzibar slave trade.

Freddie Mercury's childhood home is now a monument to the iconic Queen rockstar.

In Zanzibar, a historic 19th-century palace is a reminder of the world's shortest war.

Designed by Buckminster Fuller, this relic of the 67 Expo survived fire and ice.

This Gothic-style church is reputedly built atop the remains of one of Jesus's apostles.

The painted and decorated towers of this Hindu shrine were once the tallest structures in one of the oldest cities in India.

This modest marker near Notre Dame identifies the very center of Paris.

A daring D-Day assault by U.S. Army Rangers is commemorated atop the high cliffs of this strategic point.

A memorial to the nearly 10,000 American soldiers laid to rest on the beaches of Normandy during WWII.

This enormous "cloth of the conquest" depicts the Norman invasion of England in mind-blowing detail.

Northern Ireland's Brobdingnagian stepping stones.

A stunning Victorian abbey and walled garden on a lakefront.

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