This enormous steel tube is the biggest speaking horn in the world.

One of the tallest buildings in Africa provides a great view of Johannesburg's unique geography.

The haunting beauty of this little-visited wreck makes it a true hidden treasure.

A growing popular hipster market with over 100 local specialties and live music.

A historic hotel with many stories of haunted activity.

City Council meetings still happen in this historic building, impeccably preserved on the inside.

This Seattle store is packed with all sorts of curious creatures and creations.

Mysterious heaps of stones dot these otherworldly woods.

The former Nazi Germany concentration camp stands as a museum to remember this dark chapter in European history.

An underground city of salt.

This sprawling concrete suburb of Kraków was designed by the Soviet Union as the model proletarian city.

St. Mary's features one of the most spectacularly decorated cathedral interiors in all of Europe.

Longest fortress system anywhere in Europe.

A burial vault located under Tiber Island in the middle of the Italian capital.

The ruins of an abbey believed to have been founded by Charlemagne in the 9th century.

This gallery commissioned by Cardinal Spada is known for its magnificent optical illusion.

Roman-era ships unearthed...

A treasure trove of Renaissance-era funerary art in a Roman church built on top of Nero's grave.

This hidden rooftop garden in downtown London offers a quiet respite from a bustling city.

This museum is dedicated solely to this millennia-old handheld cooling device.

An unsanctioned shrine that sprung up outside the late singer's home is causing a stir in London's Highgate neighborhood.

Bored potato-guarding Nazis etched their thoughts onto a brick storage building in Copenhagen's Meatpacking District.

A novel collection of medical curiosities housed in an 18th-century surgeon training academy.

A collection of noses tucked inside an art museum reveals how times have changed.