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

A little slice of Japan and its aesthetics in London's Holland Park.

A vast overgrown cemetery, once known as one of London's "Magnificent Seven."

Eighty million natural history specimens call this gargantuan museum home.

This ancient structure appears Roman, but was constructed during the 16th century and was utilized until 1911.

Backwards hour and minute hands and a timing mechanism that fluctuates with the temperature led to this clock tower's local nickname.

This Byzantine Church was moved from Paris to Athens block by block.

What once sat in the world’s spotlight is today a largely disused ghost complex.

The hallucinogenic center of the ancient world.

A lonely medieval monastery on an uninhabited island.

A solemn reminder of the infamous World War II war crime that massacred almost all the men in a small Greek town.

The historic tower houses of this nearly abandoned Greek town have been compared to the spikes on an iguana's back.

This town named for the ancient God of War is home to fewer than a thousand people, but it's the birthplace of the Greek Revolution.

The Greek War of Independence was declared at this medieval Byzantine sanctuary.

The nuns here cultivate silk to weave some of the finest scarves in the world.

The ruins of an abandoned medieval city where the last Byzantine emperor was crowned.

This 15th-century island fortress later served as home to the executioners no one wanted to live near.