Europe's official "zero-level," the equator of elevation.

The former home of a mad diplomat is said to still be marked in bloody, arcane scrawls.

A line number in Amsterdam that will likely never be used again due to its tragic history.

A beautifully eclectic mix of architectural styles.

Despite the name, this 16th-century structure in Galway wasn't built by the Spanish.

Tiny silver and copper fish set inside blue-green lights are like windows to the underwater world.

A well-worshipped shrine to the Virgin Mary nestled inside the last of Zagreb’s historic gates.

An inverted staircase above the entrance to the Bethnal Green Underground Station functions as a memorial for people who lost their lives during the worst civilian disaster in the U.K. during World War II.

The bridge is a secret gallery of discarded gum that has been transformed into miniature masterpieces.

This macabre painting of a Shakespearean scene looks like something out of a nightmare.

A tiny replica of the iconic London landmark hides on the side of the steel structure.

The Art Deco artwork depicts gilded carriers of deadly illnesses.

Originally built for London’s cab drivers, this bright green hut now serves anyone a hot drink or meal.

Black cat statues guard this temple-like Egyptian revival factory.

The remains of the great moral philosopher reside in a university in London.

The "beautiful" equation predicting the movement of all electromagnetic particles is engraved in front of Newton's tomb.

It holds a fabulously designed tribute to astronomer Edmond Halley.

At almost 1,000 years old, this is the oldest known door in all of Britain.

The niches over the western entrance of Westminster Abbey honor individuals from the 20th century who gave their lives for their Christian beliefs.

A statue of the legendary Celtic warrior queen who fought the Roman invaders stands in one of the cities she once destroyed.

Originally meant to hold a statue of King William IV, this support sat empty for years. Today, it hosts a rotating cast of public artwork.

A mysterious shape catches the eye in this 16th-century painting.

A quartet of tiled art pieces adorn the floors of this prestigious art museum.

These official units of measurement—including chains and perches—lie hidden beneath tourists' feet in a popular London hub.