A plaque hidden in the law faculty at Leiden University honors the first scientist to make liquid helium.

This 11th-century castle sits so low you can't see it behind the surrounding buildings.

This giant radio telescope would be a rusting ruin if it hadn't become such a beloved relic.

This giant wire frame man sculpture is crouched in contemplation.

A trio of red, white, and blue stones embedded in the streets of Leiden are markers of medieval territory and law.

This enormous storm barrier is one of the largest moving structures on Earth, with each arm taller than the Washington Monument.

A set of 27 bamboo tubes creates an eerie soundscape that changes with the wind.

A preserved building where the dead were once watched for signs of life.

This centuries-old gothic monster has been converted into a sprawling, glossy bookstore.

One of the dwarven trees dates back to 1625 and survived the Hiroshima bombing.

Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

London's smallest police station is barely the size of a phone booth.

An alleyway plaque is all that remains of the independent Texas' envoy that forgot to pay their rent for over a century.

An easily overlooked stretch of ornate window fronts and gaslight lamps that could be right from the pages of Dickens.

An unusual round church in London with a Templar past.

This churchyard arbor is surrounded by hundreds of gravestones placed there by author Thomas Hardy.

A bridge destroyed three times: once as a ruse, then in an actual attack, and finally for the movies.