This Bronze Age tomb is the centerpiece of a clearing within a beautiful Irish forest.

A measuring mishap led to these artificial stone ladies losing their stomachs.

This mine is home to the largest man-made hole in Europe.

For the holidays, the tallest broadcasting tower in the Netherlands turns into one of the world's tallest Christmas trees.

What looks like a normal building is really a hollow facade hiding a subway vent.

Once a 19th-century brasserie, this McDonald's exterior celebrates Alsatian design and the "King of Beer."

This innocuous-seeming building is actually the remnant of a major wartime brothel.

Behind the pink curtain, Au Bonheur du Jour, an art gallery of erotic archives.

A grotto-like lodge decorated with gilded mosaics, rocks and a noisy waterfall was the setting for the most sumptuous pleasure house of 1900s Europe.

This off-limits room in the National Library of France is home to a system of pneumatic tubes, once used to bring books to readers.

This massive library holds what was once the largest book collection in the world.

This small, ingenious cannon once helped regulate Parisian life.

Noirish green neon marks the location of one of the oldest private detective agencies in France.

High atop the Eiffel Tower is a small apartment built exclusively to entertain the science elite and make the rest of Paris jealous.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

Paris' linguistic guide to the international language of, yes, love.

The remaining relics of the patroness of Paris lie in a chapel under a striking double spiral staircase.

19th century pendulum and a clock restored by a rogue group of guerilla artists.

The video game-themed street art first popped up in the French city.

A surrealist timepiece by the artist of melting clocks.

Abandoned railway line circling the city of Paris.

The tradition of open-air secondhand and antiquarian bookselling in Paris dates back to the Renaissance.

Created as a "model concentration camp" to hide Nazi atrocities from the international community, this former camp-ghetto now holds a museum and memorial honoring the lives lost within.

Climb inside an iron crystal magnified 165 billion times its normal size.