This bridge later moonlighted as a local jail.

This rock was donated to the museum by an inspired young visitor.

A unique sculpture cemetery dedicated to the region's defunct businesses.

This statue includes the molehill that toppled a king.

This original castle in Kendal is 1,000 years old.

Before firefighters, villagers relied on this simple hook to save their thatched cottages from a fiery doom.

A rare example of a building constructed specifically for catching eels.

One of the most studied Iron Age settlements in Europe.

This holy spring and its well have been the site of religious devotion for millennia.

Hidden in a grotto 26 feet below Nottingham's oldest hotel, this stylish subterranean drinking den is notoriously hard to find.

A hands-off space for graffiti artists to hone and display their skills.

The signs of a long buried road can still be found hidden beneath a London sewer grate.

This wildly-tiled artist's palace is a living and growing account of the creator's life, loves, and labors.

Wedged between two buildings at the Great Ormond Street Hospital is this secret music installation.

In this cobwebbed old operating theater, you can practically hear the screams of the unanesthetized patients.

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

An unusual round church in London with a Templar past.

A historic London pub with prison cells in the cellar and a "spy room" on the second floor.

This Wall Street bar was once a hub of revolutionary activity where Washington famously bid farewell to his troops.

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

A garment factory hides a small Dominican eatery in the hallway to its freight elevator.

The remnants of two World's Fairs are here, complete with a 12-story globe, a mini-Manhattan, and a UFO-shaped pavilion.

A treasure trove of artifacts, books, and artwork from the "golden age" of exploration.

Amid the bustle and noise of the Financial District hides a secluded garden oasis above the city streets.