Amsterdam's narrowest house facade is a monument to 17th-century tax evasion.

Europe's official "zero-level," the equator of elevation.

A Dutch passageway's artistic, aquatic-themed makeover pays tribute to the capital city's famed waterways.

This unattributed sculpture in Amsterdam is hiding in plain sight.

The last of Amsterdam's original sea level markers remaining in place.

Famed for its pie, this eatery has a hidden tunnel that allowed Catholics to secretly walk to church during the Reformation.

A floating cat sanctuary on an Amsterdam canal.

Where royalty waits in the height of luxury.

This London pub hides a peculiar secret: a recreation of the rooms shared at 221b Baker Street by Sherlock Holmes and Dr. Watson.

A living memorial to the trees London lost during the Great Storm of 1987.