Scattered throughout London are ancient remnants of the city's former bounding wall.

A cluttered and astounding collection of antiquities and curiosities.

A 2000-year-old Roman amphitheater lies just below Guildhall Yard.

London's smallest police station is barely the size of a phone booth.

An incarceration museum on the spot of possibly the oldest prison in England.

Hear the quietest sound from across the dome.

The anatomical-pathological collection of a man who changed surgery.

Catacombs turned marketplace.

A 1,215-foot tunnel transports pedestrians beneath the River Thames.

Eighty million natural history specimens call this gargantuan museum home.

One part local history, 99 parts gruesome haunted house.

An unusual round church in London with a Templar past.

This London pub hides a peculiar secret: a recreation of the rooms shared at 221b Baker Street by Sherlock Holmes and Dr. Watson.

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.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.

The picturesque birthplace of Icelandic democracy is drenched in the blood of its brutal past.

This natural Icelandic fissure allows divers to swim right between two volatile tectonic plates.

If a glacial river suddenly diving into a sheer chasm via a dramatic, multi-stage waterfall isn't peak Iceland, it's certainly close.

This valley of hot springs and boiling mud pots is home to the record-holding "Geysir," which originated the English word.

A winding, blood-red tunnel of hardened lava navigable by foot.

An encyclopedic collection of mammal penises.

This elegant arc of a waterfall marks a religious turning point.