Two very green residential towers cleaning the air in one of Europe's most polluted cities.

Italy's curious field of mud volcanoes is named for being both gross AND salty.

This 2,000-year-old Doric bridge is still open to pedestrian traffic to this day.

An ancient monastery, a locked room, and a mysterious book heist.

The elaborate clockwork contraptions in this Scottish gallery create small worlds of whimsy and horror.

Old-fashioned knowledge and modern engineering create the world's only rotating boatlift.

A top-secret bunker now turned museum, is an eerie look at what life would have looked like in the event of nuclear war.