See what remains of a once grand ancient Roman circus.

The secret medieval communication system will whisk your words above the noise of the crowd.

This grisly effigy displays an early Christian martyr who was skinned alive and beheaded.

Rare and wonderfully wormy cadaver art captured in brass for centuries.

An enormous steel waterfall is a nod to the substance that shaped Britain's Steel City.

A rotting air force base is now home to rare birds and scarce plants.

A gorge full of caverns where early humans lived alongside cave hyenas, giant mammoths and wooly rhinoceroses.

This ruined medieval castle was the scene of Lord Robert Dudley’s seductive reception for Queen Elizabeth I.

One of the earliest large-scale "hyper" roofs in the U.K. is now a derelict roadside attraction.

The undercroft is a spectacular example of medieval Cistercian architecture.

This memorial pays homage to the Royal Air Force squadron that breached two important dams during World War II.

This little-known hero has been protecting "The Fens" for close to 400 years, and now from its most powerful challenger yet: climate change.

Hundreds of huge, centuries-old horseshoes adorn the walls of this nontraditional 12th-century castle.

The shop where the girl who inspired the beloved character once bought sweets is now a book-themed commercial curiosity.

The dance of this huge clock is a magnificent and eerie commentary on good and evil in the history of humankind.

Britain’s longest ancient monument, this great 8th century earthwork was built to mark the boundary between what would become England and Wales.

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

Hidden in plain sight, this creepy sculpture watches from above.

The London statue that imitates passersby.

This South London cemetery holds the remains of more than 15,000 people.

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

Peek inside restored planes at this off-the-beaten-path collection of aviation archaeology.

The sanctuary seems to either float atop the water or sink into the dirt, depending on the water level.

A clumsy-looking flying locomotive rusts within sight of a busy rail station.