Spain's stunning solar energy plant.

A moving memorial to the fallen and missing from WWI trenches.

Elevated freight railway turned wildly successful urban park.

The celebrated eyesore created by starry-eyed sweethearts.

Hidden beneath the streets of London is a secret subway that only carried mail.

The heads of two giant mythological water horses honor Scotland's horselord past.

Old-fashioned knowledge and modern engineering create the world's only rotating boatlift.

A favorite with sightseers, this Norwegian funicular provides easy access to a stunning view of Bergen and its environs.

Man-made mineral caves house massive bat colony.

The ruins of an Estonian prison are drowning in the quarry lake where the convicts were once forced to work.

A decommissioned submarine base makes a great space for graffiti art.

These tombs were built into the side of a mountain so that ancient angels could reach the dead.

The stately remains of Llywelyn the Great's mighty fortress.

A miniature Italianate fantasy village on the coast of Wales and the set of ITC classic "The Prisoner."

The remains of centuries of copper mining appear like an alien landscape.

This Welsh village gave itself a ridiculous name in a publicity stunt a century ahead of its time.

Whisper secrets in a busy station only to be heard on the other side of this acoustic arch.

Join in a Seance at the Swedenborgian Church.

This historic address is home to the beloved ball and is an almost totally empty building among the most expensive real estate in the world.

The New York hotel where tragic visionary Nikola Tesla spent his final hours, destitute and alone but for the pigeons.

This hilarious English intersection is an automotive whirlpool.

Famously misunderstood wonder of the ancient world

The deepest metro station in the world.

340-foot statue built to honour the Heroes of the Soviet Union.