An off-the-beaten-path boutique stuffed with an eclectic collection of upcycled goods.

France's national museum of scientific and industrial instruments.

The railway carts travelers to central Athens's highest peak, which offers stunning vistas of the city.

This remarkably well-preserved Egyptian plinth is pretty well traveled for a giant piece of stone.

Climb a steep hill in 90 seconds on the second-oldest urban subway in the world.

Ancient serpentine sacrifice holder that has stood the test of time.

A fountain standing as a testament to a doomed alliance.

This crucial gathering spot along the "hippie trail" still displays old notes between traveling beatniks and backpackers.

A gorgeous, Gaudí-esque stairway constructed in the city of Istanbul by a prominent Jewish family.

This column celebrates Rome's victory over the Goths, and may be the oldest Roman monument in Istanbul.

This half-forgotten fortress was constructed by the Ottoman conqueror of Constantinople.

Taking the subway here means doing so over a bridge located in the middle of an estuary.

A surprising and unconventional mosque hidden in the subsoil of Istanbul.

An expansive complex of subterranean tunnels is all that remains of one of Europe's most formidable medieval fortresses.

An ultra-modern diversity park in Denmark has turned an entire city block electric pink.

Copenhagen's celebrated theme park and gardens.

This sublime architectural marvel is a rare example of an expressionist church.

The de facto symbol of Copenhagen is this bronze fairytale which cannot seem to keep its head for very long.

Hans Christian Andersen for the postmodern world.

The gilded, masterful astronomical clock will calculate time, dates, and planetary positions for thousands of years to come.

Beneath Denmark's Højbro bridge, a bronze merman and his seven sons forever mourn for the mother and wife who left them for land.

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

The world's first combination ski slope and power plant.

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