The first geometric self-supporting spiral stairs in Britain are a truly beautiful sight.

The watery entrance for condemned prisoners heading to the Tower of London is still visible along the Thames.

Hear the quietest sound from across the dome.

The perfectly preserved underground rooms where Churchill plotted the war against Germany.

The popularity of Sherlock Holmes led to the creation of his fictional address, turning the orderly London street numbers askew.

Kings Cross Station pays tribute to its role in Britain's best-selling book series.

Historic medieval fortified city in southwest France.

Red, white, and blue painted steps along with a Union Jack celebrate the outcome of Gibraltar's 1967 referendum.

This bronze boar's snout has been rubbed to a golden sheen by visitors seeking good fortune.

Brass cobblestones mark the places where individual Holocaust victims were taken from their homes.

The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.

From Tintin to the Smurfs, Europe's greatest graphic icons are celebrated in a grand Art Noveau gallery.

A museum dedicated to the alleged Roswell Incident.

Originally used to sell brandy, the bull-shaped billboard became an iconic symbol of Spain.

For decades, Puerta del Sol has been illuminated by a giant, guitar-wielding bottle of sherry.

This magnificent castle grew from a small Moorish fortress, and reportedly inspired two iconic Disney castles.

A stone slab in Madrid marks the point from which the distances of Spain's national roads are measured.

The iconic boulevard is the perfect place to catch sight of a bicycling skeleton, a levitating Satan, or a chef with his head stuck in a pizza.

One of the few remaining ancient aqueducts described by Frontinus as 'the most solemn testimony of the Empire.'

Giant eggs, walls of bread, and nightmare surreality mark the largest collection of works by Salvador Dalí.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

The celebrated eyesore created by starry-eyed sweethearts.

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