This mysterious marker puzzles pedestrians and infuriates geographers.

Rome's first modern graffito is all that is left of a peaceful protest from the 1970s.

The former home of an Italian artist is now a shrine to his ambitious works.

Also known as the Square Colosseum, this building is a prime example of fascist-era rationalist architecture.

A detailed pachyderm supports Rome's smallest Egyptian obelisk.

More sculpture than building, this architecturally significant temple was built on the spot of Saint Peter's crucifixion.

This ritzy Italian market is built around a statue of an unforgiven heretic who was burned for his belief in an endless universe.

Rome's semi-secret peephole vista is also a former Crusader stronghold.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

The yawning maw of this pagan visage is said to bite off the hands of liars.

The remains of what was once the world's steepest passenger funicular.

100 massive sculptures in the Hudson River Valley.

This huge pile of volcanic boulders hides a stunning network of secret grottoes.

This monument on Breed's Hill proves that one of the most famous battles of the Revolutionary War is misnamed.

From bench to vandalism to art, this silly prank seat was funny enough to become permanent.

Ice cream stand, snack bar, and time capsule of milk conveyance.

This upscale streetwear store is hidden behind a fake Snapple machine in the back of a deli.

An enormous, inside-out glass globe built in 1935.

The only structure left with direct ties to the Salem witchcraft trials of 1692.

Golden and naked, the figure that was once the highest point in New York is all that remains of the second Madison Square Garden.

Philadelphia boasts one of the best — and most often overlooked — traditional Japanese gardens in North America.

A layered tribute to the work of mosaicist Isaiah Zagar.

The 80-foot tire that looms over Michigan's I-94 was once a Ferris wheel in the New York World Fair.

Detroit’s Eastern Market has been transformed into an outdoor museum with colorful murals that address social issues and symbolize the city.