The decaying ruins of Wales' first asylum for the mentally ill.

Just a few miles off the western coast of Ireland lies an isle steeped in Irish literary history.

An eccentric garden of sculptures crafted in India decorate an Irish green space dedicated to Alan Turing.

Catholics make up 84% of Ireland's population but this Dublin museum remembers the small but important Jewish community.

The oldest public library in Ireland.

The ancient tomb acts as a calendar that keeps perfect time.

An ancient neolithic tomb that only sees the sun twice a year.

A sacred well steeped in Pagan roots on the West Coast of Ireland.

A remarkably intact castle that once was the largest in Ireland.

This floating garden in the sky is straight out of a fairy tale, but the real thing is nothing short of magical.

The bomb-ravaged remains of of a colossal Neptune.

Abandoned medieval hill town.

This former fascist summer camp was abandoned for decades.

Giant, pink stuffed rabbit on an Italian mountain.

Home to items never before seen by the public.

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

Parking garage where Bob Woodward met Watergate source "Deep Throat."

A secretive collection featuring objects that were designed specifically for U.S. intelligence operations.

The remnants of a wooden-hulled fleet built and abandoned in WWI, now home to a thriving ecosystem.

An organ located deep within a cave, whose "pipes" are the geological features of the cave itself.

The remains of a failed attempt at medieval nerdery are hidden deep in the woods of Virginia.

A bunker "with enough U.S. currency to replenish the cash supply east of the Mississippi" in the event of nuclear war now protects nitrate film.

America's post-nuclear-attack chambers of Congress.

A sacred site for Native Americans surveyed by George Washington and owned by both King George III and Thomas Jefferson.