The world’s narrowest house makes for an awkward, four-foot-wide living space.

This mural painted by Keith Haring was done without payment as a gift to entertain the children at the Hôpital Necker.

This emotive sculpture was originally created for the 1878 World's Fair.

A mud statue stands in the dark tunnels, seeming to hold up the weight of the city above.

The oldest and smallest cemetery in Paris is only open to the public twice a year.

The spiral staircase hidden inside this giant Parisian column was likely built for Catherine de Medici's astrologer.

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

These lesser-known Maltese catacombs date back over 1,700 years.

The floor of this spectacular Baroque sanctuary is covered in memento mori.

The broken skateboards that became a poignant memorial to a murdered skater.

Wedged between two buildings at the Great Ormond Street Hospital is this secret music installation.