Legend says if this neo-Gothic basilica is ever officially completed, the world will come to an end.

This iconic 1958 tower welcomes air travelers to Tucson with neon-lit letters and architectural style.

Situated on a sacred Inca site, this 16th-century cathedral took nearly 100 years to build.

This 18th-century sundial was designed to calculate the date of Easter each year.

This geometric feat is a testament to the Incas' mesmerizing architectural abilities.

A monument to the three wars that led to German unification towers within a Berlin traffic circle.

The most loyal of little dogs, or a Victorian era publicity stunt?

A network of bells in the pubs and restaurants around Westminster alerts politicians when it's time to cast their votes.

The Metropolitan Police refurbished the blue box (perhaps not coincidentally) the same year "Doctor Who" returned to TV screens.

A 16th-century fountain marks the site of a lost medieval cemetery once filled with mass graves.

Jesus' footprints and the first catacombs in the world.

2300-year-old Roman road connecting the empire.

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

Historic medieval fortified city in southwest France.

This enormous "cloth of the conquest" depicts the Norman invasion of England in mind-blowing detail.

Explore this medieval cathedral by trying to spot all the malevolent monsters hiding in its beautifully colored windows.

This demon atop the Notre-Dame de Paris looks utterly bored.

Featuring the the longest lift span of any vertical-lift bridge in the world.

Once in a state of dilapidation, this candy-inspired fortress is now being revived.

Tucked behind New Jersey's abandoned Gingerbread Castle lie the eerie ruins of a once-flourishing paper mill.

An image of the legendary saint stands in the shadow of a cathedral she liberated.

The walls and streets of the ancient city are peppered with penises.

Quito's historic, main square dates back to the 16th century.

Hidden in plain sight on a pair of Manhattan subway tunnels are a pair of public instruments that sing to each other.