Human-made caves excavated to hide a secret society of wealthy pagans.

This small square basin behind a quiet church was once a popular medieval pilgrimage site.

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

This pedestrian walkway cuts through a cemetery and over several burial vaults.

The castle still holds traces of the abandoned Roman fort it was built atop.

Beasts and branches swirl in sandstone carvings, interrupted by one strange creature.

This effigy was crafted to annoy a neighbor after a civil dispute over a foul smell.

A baffling beast so absurd a town councilman called it "intellectual vomit in technicolor."

Scotland's oldest medieval bridge is also among the last reminders of early medieval Aberdeen.

The oldest church in Inverness witnessed the brutal executions of many Scottish soldiers.

A memorial to two dedicated postal workers who lost their lives delivering mail.

Where the Border Reivers of the Johnstone clan used to hide their stolen cattle.

“It has nae lugs!”

This hidden rooftop garden in downtown London offers a quiet respite from a bustling city.

A sculpture of a partly-buried Roman helmet commemorates a North Wales town’s connection with its Roman past.

Roman ruins found on the outskirts of a small town on the North Wales coast have over time become a strong part of the community's identity.

The ruins of a stone tower with alleged (but unlikely) Roman origins.

An Irish cemetery filled with victims of political strife and violent conflict, including the grave of Bobby Sands.

These engineering masterpieces are a dominant feature of the Belfast skyline.

A museum marks and documents the site of the Titanic's launch.

These murals stand as reminders to the troubled history of this Northern Ireland city.

The whimsical twist of this spire was either caused by the Devil, an unexpected virgin, or lead.

A secret meeting in this small cottage changed the course of British history.

The oldest surviving glass furnace cone in Western Europe.