This banal Parisian entranceway is not what it seems.

The first green space constructed on an elevated viaduct.

Abandoned railway line circling the city of Paris.

This jam-packed Singapore antique museum preserves the fading remnants of a uniquely mixed culture.

Singapore's landscaping project is home to 18 incredible Supertrees.

When a supermarket opened up shop within a medieval building it became protected by UNESCO on a technicality.

This picturesque medieval monastery guards a small trove of historic treasures.

Once a state-of-the-art tuberculosis treatment spa, these ruins are now ruled by paintball players.

Legend has it fairies gathered at the site of this medieval castle.

Yugoslavia's biggest underground airport lies in ruins.

This stunning, out-of-the-way Croatian monument commemorates a community's uprising against occupying fascist forces.

Where the lovelorn find a home for their sentimental keepsakes.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

A museum dedicated to the former country.

Ride in 1960s style on the private luxury train Marshal Josip Tito used to travel around Yugoslavia.

Nikola Tesla's ashes are held in a golden sphere, surrounded by his works.

One of the best collections of wax anatomical models in the world.

An ornate private entrance to the Vienna subway built specifically for the emperor.

The housing complex served as an anti-fascist fortress during the Austrian Civil War.

This museum promotes informed contraception by documenting its often secret past.

Beautiful Austrian natural history museum with carved ceilings and row after row of ancient taxidermy.

Located right outside of Vienna, visitors can take in expansive views of an ethereal forest.

The former private quarters and office of Dr. Sigmund Freud now hosts a museum housing the works of the founding father of psychoanalysis.

Handsomely crafted representations of our round planet.