This volcanic plug boasts the longest recorded history of any Scottish stronghold.

The ornate structure is part of a building boasting more marble than the Vatican.

This charming Latvian lane doubled as Baker Street on the Soviet Union’s version of Sherlock Holmes.

This colorful and fiery mural depicts the Irish folk story of the beloved hero Cuchulain.

Graffiti from the 16th and 17th centuries cover the walls of this part of the Tower of London.

Looking strangely like Rome's Colosseum, this unfinished tower has dominated the skyline for over 100 years.

Climb to the top of its spiral spire for spectacular views of Copenhagen.

Once one of the largest rooms full of books in the world, this bookstore basement is still a treat for bibliophiles.

Flames have been burning within this mountain for more than 2,500 years.

An urban megalith steeped in local lore.

This 135-year-old weather station studied the effects of the climate on human health.

This massive monument has been telling the time for 150 years—at a slight angle.

The only monument to name all of the passengers and crew who died on the RMS Titanic.

A wonderfully eccentric Victorian-era museum and library.

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

The largest salt lake in the Sahara is mysteriously alluring.

This popular cave pool is truly magical, despite the crowds.

This two-legged horse statue celebrates a beloved cartoonist and his quirky characters.

The only pub in the world surrounded by an ancient stone circle.

Local legend says Isaac Newton built this footbridge without any screws, bolts, or nails.

Journey through this open museum where even employees remain true to period.

The ancient heart of Tunis is an enormous maze of narrow streets and alleyways.

A small island with shimmering pink sands, home to loggerhead turtles and rare plants.

A community of artists and entrepreneurs seeks a simpler life on London's waterways.