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

Copenhagen's celebrated theme park and gardens.

This memorial commemorating fallen Swiss Guards of the French Revolution has been called the saddest stone in the world.

This historic covered bridge contains a series of macabre paintings that communicate one thing: everyone dies.

The bears of Bern have been a city highlight for over 500 years.

Two very green residential towers cleaning the air in one of Europe's most polluted cities.

This fairytale castle was built as a show of power but was nearly torn down thanks to its history of torture.

A little sculpture with a large wardrobe.

Cozy basement bar sports an inventory of over 2,000 beers.

This small city where almost everyone lives in the same building can only be reached via North America's longest tunnel.

Running under an entire mountain, the longest highway tunnel in North America is kept fresh using portal fans and jet fans.

An Alaska livestock farm devotes itself to harvesting wool from creatures that once ran with mammoths and sabertooth tigers.

The design of this historic domed church was influenced by Thomas Jefferson and intended as a statement of religious freedom.

Rediscovered after a century, the father of the American Navy was reinterred in something dredged up from Davy Jones’ locker.

At Washington's Dulles Airport is a satellite museum (no pun intended) with three quarters of a million square feet of aircraft history.

A priceless collection of the Nation's cryptologic history.

America's first federal monument.

Once home to seven different roller coasters, Glen Echo has undergone many transformations since its founding in 1891.

This stately building in Alexandria, Virginia was built by Freemasons to honor one of their most famous members.

A former major munitions plant that has been converted into a sprawling art space.

This isn't your average roadway—it's actually a National Park and a transportation pioneer.

The Corinthian columns that towered over Abraham Lincoln’s inauguration stand proud.

The privately owned cemetery that holds room for Washington's finest when they step down from life.

Soldiers were buried next to Lee's house in the center of Arlington Cemetery to dissuade the general from reclaiming his property after the war.