Much has been written about the Duomo di Milano one of the largest Gothic cathedrals in the world, but Mark Twain, perhaps, described the marble church's beauty best, in his 1869 classic "The Innocents Abroad:" "A very world of solid weight, and yet it seems in the soft moonlight only a fairy delusion of frostwork that might vanish with a breath!"

Most of that airy appeal is conveyed in the church's exterior 135 elegant spires and 3,400 intricate statues grace the building. In true Gothic style, the ambience of the interior is rather dark thanks to the stained-glass windows and heavy stone columns. Not to be missed is a schlep up the stairs (or catch a lift up on the elevator) to access the rooftop terraces. Here, surrounded by the cathedral's eerie marble towers, you can see across Milan, all the way out to the peaks of the Alps.