A hidden church in a hidden courtyard tells the story of the Miracle of Amsterdam.

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

At Monet's beloved home you can still see the Japanese bridge, waterlilies, and weeping willows that were the subjects of some of his most iconic paintings.

Lyon's "Wall of the Silk Weavers" is one of the largest murals in Europe.

Hundreds of hidden passageways weave through the old quarters of Lyon.

For hundreds of years, automatons moving to metallic music have been marking the passage of time.

Lyon, France is home to two remarkably preserved Roman theaters, one dating back to 15 BCE.

Sky ships, planes, and portraits left as unique tokens of hope and thankfulness.

Men in rubber-soled boots serve as your "brakes" on this toboggan ride Hemingway described as "exhilarating."

A contemporary art installation housed within a Gothic cathedral.

Holy Grotto of Montserrat Monastery holds one of Europe's mysterious black Madonnas.

This home designed for chocolate magnate Antoni Amatller is an exquisite treasure-box of Catalan Modernism.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

The 2,000-year-old Roman columns are hidden within Barcelona's Gothic Quarter.

The iconic boulevard is the perfect place to catch sight of a bicycling skeleton, a levitating Satan, or a chef with his head stuck in a pizza.

The final resting place for Bermuda's British military, including a man who died of sunstroke.

Once a strategically imperative naval base, portions of this Bermuda dock complex now serve cruise ships.

The world's smallest drawbridge.

A dark patch of the ceiling at Grand Central Terminal which was not restored is still stained brown by tobacco.

Rumor has it the uncarved lump behind the three famous suffragists is reserved for the first woman president.

A little marble compass above George Washington's (empty) tomb in the Capitol marks where D.C.'s four quadrants intersect.

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

The most decorated dog of World War I is preserved in the Smithsonian.