Hidden behind a YMCA stands the remains of a ceremonial site that dates back hundreds of years, whose ground is still considered sacred to many Hawaiians.

A defensive structure built during the Hundred Years War has remained useful in one way or another for nearly 700 years.

A Victorian-style home known as the “Castle on the Hill.”

At the edge of the high desert, California's second-largest natural lake is home to a unique subspecies of trout adapted to its alkaline waters.

On a hill overlooking Loch Trool, a granite boulder marks the site where Robert the Bruce, King of Scotland, defeated an English army.

This unusually-named reservoir found a second life as a nature preserve.

Never actually a tree at all, this spot was the site of London's public hangings for nearly 600 years.

This long-hidden space above Westminster Abbey now displays the battle gear of the legendary King Henry V.

A relic of Victorian grandeur hides beneath a busy South London road.

The plunge pool is a surviving relic of a rowdy royal residence.

The commemorative stone column conceals a secret laboratory.

Behind one of the world's most impenetrable vaults is a massive collection of retail silver.

Its collection includes a broad array of social, geographic, graphic design, and political history.

The pockmarks across the building's facade are remnants of the Blitz.

A hidden path at the National Theatre lets you look behind the scenes of the latest productions.

The ritual has been performed uninterrupted for nearly 700 years.

This ancient Egyptian obelisk still bears the wounds of World War I.

This once-controversial and slightly confusing statue of Achilles was built out of captured cannons.

The bronze uniforms commemorate the vital role of women during World War II.

A plaque pays tribute to the artist's longtime London home.

A 1950s beatnik coffee house, turned 60s counterculture hotspot, turned modern music venue.

These wire animal sculptures commemorate the exotic inhabitants that once called the Tower of London home.

The Great Fire of London and the regulation of one-way streets both started in this alley.

These marks in Myddelton Passage aren't your run-of-the-mill vandalism, and they weren't made by your typical vandal.