This eye-popping Icelandic crater lake is surrounded by red volcanic rock.

The remains of a magnificent medieval fortress that was the capital of a vast empire.

Constructed during the 7th century this is one of the oldest largely intact Christian churches in England.

The one-time watch house for incoming ships at the Golden Gate now stands abandoned and hidden in trees.

Tell this pair of "love-inviting" cats in Ginza your romantic hopes.

There's an exclusive Beefeaters pub hidden in the Tower of London.

This centuries-old Italian chapel hangs midway down a sheer cliffside.

The blinking light atop the iconic landmark has been sending secret messages for decades.

This ordinary street was made infamous by a legendary visit from the devil.

Hidden in plain sight on a pair of Manhattan subway tunnels are a pair of public instruments that sing to each other.

This medieval sanctuary's tree-framed door looks like a portal to a mythical realm.

It was an experiment to prove that glacial boulders and rocks can be used in constructions and dwelling.

Just your average Marie Antoinette–themed speakeasy in an abandoned 19th-century subway tunnel.

A 19th-century subterranean reservoir repurposed as a contemporary art cave.

A creepy statue of a hooded ghost hauls itself up from the water in a historic Lithuanian city.

Originally intended as a temporary installation, this sculpture is now a permanent part of a stunning Scottish beach.

These quaint cottages feature built-in signaling devices for fishermen.

A museum of carnival attractions where you are invited to ride the rides.

Manhattan’s Battery Park has a whimsical carousel full of spinning, glowing fish.

This alley off Edinburgh's Royal Mile contains remnants of the city's seedier history.

At the right time of day, sunlight floods through the roof of this cave and illuminates the small pavilion hidden within.

Mosaics, storks, and brothels—this ancient city has it all.

A beautiful Greco-Roman structure houses a well once believed to have healing powers.

The most remote tree in the world is more than 170 miles from its nearest neighbor.