Bristol is a quirky British city with beautiful hilly vistas and plenty of historic sights to explore. Anyone interested in ships will have a blast aboard Brunel’s SS Great Britain, the world’s first great oceanliner, and the Matthew, a replica of the ship upon which John Cabot sailed to America in the 15th century. The graceful Clifton Suspension Bridge is another must-see.

Catania has been a prize of many empires over the centuries, from Greeks to Romans to Arabs to Normans to Spaniards (to name a few). But its citizens have a more dangerous enemy right in their backyard—Mount Etna, Europe's largest and most active volcano, which destroyed the city with earthquakes and lava flows in 1693. Look closely at the baroque buildings dating from after the eruption—you'll notice a creative use of lava.