Rome's semi-secret peephole vista is also a former Crusader stronghold.

Hidden within this iconic mountain are a set of World War II bunkers once used by German forces.

You can still find treasures on the pebbly beaches of one of the world's oldest jade-producing areas.

A shrine dedicated to the sacred white snakes of Iwakuni, whose albinism has been passed down for generations.

Denmark’s never-ending bridge.

This caldera was once associated with the Etruscan god of the underworld.

This medieval mountain town is also known as the "Village of Streams."

Narrow passes cut out of mountains surround the medieval capital of Japan.

This Kyoto Starbucks takes coffee drinkers back in time.

Discover the past, present, and future of packaging in this unique Japanese museum.

Hang out with thousands of butterflies in one of the world's largest such enclosures.

Holy Hindu shrine in an enormous, monkey-filled limestone cavern.

Malaysian fireflies create a dazzling display as thousands light up in unison.

One of the largest caverns in the world has a maw large enough to stack cathedrals in.

These jagged limestone blades cut out through the canopy of the jungles of Borneo.

This dangerous-looking suspension bridge may have been too unstable to remain open.

One of Ireland's most infamous prisons for rebels including men, women and children.

Though they've since been renamed, these two streets hint at Dublin's darker days.

The 19th-century pharmacy (now a used bookstore) was featured in James Joyce’s "Ulysses," and has changed very little to this day.

Dublin's "Dead Zoo" serves as a window to Victorian museum design.

An 80-year-old plane tree is devouring an iron bench at Ireland's oldest law school.

The gorgeous library at Trinity College is home to remarkable treasures of Irish identity.

Colloquially known as “piss alley,” this narrow street filled with tiny bars and barbecue stands looks like it was pulled straight out of “Blade Runner.”

Home to three historic ships from the age of Vikings.