A sixth-century Byzantine cistern hidden below a modern carpet store.

A small etching on the white marble parapet was written in runic script by a Viking mercenary.

A marvel of Byzantine engineering under the streets of Istanbul.

London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.

The commemorative stone column conceals a secret laboratory.

The bones of two medieval royal lions were discovered at the historic fortress.

The Kalamazoo factory has 100 years of instrument-making, and one big wartime secret.

This unassuming alcove in London’s famous Tower Bridge once served to capture, store, and display dead bodies from the River Thames.

Hear the quietest sound from across the dome.

These official units of measurement—including chains and perches—lie hidden beneath tourists' feet in a popular London hub.

The sculpture of the deceased cockatoo flops atop its personal plinth.

An architectural oddity hides in plain sight on this iconic London bridge.

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

This unique bridge curls up like a caterpillar to let boats pass and then unfurls again to span a small canal.

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

The ritual has been performed uninterrupted for nearly 700 years.

A decommissioned tube carriage within a London museum hosts a regular pop-up supper club.

This vintage "streetcar boat" lay at the bottom of Lake Minnetonka until the 1980s.

Inside this museum resides a boot fit for a giant.

This water tower has been a staple of the Rochester skyline since 1931.

An abandoned bus station transformed into a museum dedicated to the history of Greyhound Lines, in the place where it all began.

Journey through the largest remaining peat bogs in the contiguous United States to see the wilderness as it once was.

The literary king of the Jazz Age was born in this lovely Minnesota home which still honors his legacy.

The Midwest's reigning king of surplus stores is full of nothing you need and everything you want.