Architecture lovers won’t stop touching the National Gallery's 19.5 degree marble prow.

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.

"Congress may voluntarily remain in session throughout the summer, in order that our Congressmen may be protected from the intolerable discomforts and dangers of the ordinary outdoor weather!”

In the days before house numbers, these colorful signs held clues about various buildings' purposes.

A Dutch passageway's artistic, aquatic-themed makeover pays tribute to the capital city's famed waterways.

Established in 1638 to battle the Black Death, Hortus Botanicus Amsterdam is a treasure trove of rare flora.

Taste the white whiskey that the United States' first president once distilled and enjoyed.

Home to items never before seen by the public.

A tiny piece of the Moon is embedded in this stained glass masterpiece.

An overlooked memorial honoring the local Washington residents who died in World War I.

The spot in the Mile-High City that's exactly 5,280 feet above sea level (at least for now).

A Rocky Mountain city provides a happy ending for a pinto pony and his Brobdingnagian red chair.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

This historical Netherlands fortress still bears the marks of its single siege.

This centuries-old gothic monster has been converted into a sprawling, glossy bookstore.

This bike path traverses the treetops.

A magical and peaceful ruined Cistercian abbey in what is now southern Belgium.

Three floors of musical instruments coming from all corners of the world and hundreds of years of musical history.

This collection of over 50 murals celebrates Brussels' rich history as the self-proclaimed home of the "comic strip."

A little sculpture with a large wardrobe.

The world-record holder for the longest bridge stretching continuously over water.

A precariously balanced rock perches on the edge of a cliff created tens of thousands of years ago by glacial erosion.

These light, hollow rolls have been linked to Acadia National Park since the 1890s.