Just outside the old walls of Bologna, a covered walkway sets off up a hill and does not stop; it runs for almost two and a half miles, climbing all the way to a church on a ridge some thousand feet above the city, and along its entire length it is roofed, arched, and unbroken: six hundred and sixty-six arches, one after another, marching up the slope in a great brick serpent.
It is the longest portico in the world, and the strangest thing about it is the reason it exists. The whole colossal corridor was built, in the end, to keep a single small painting out of the rain. To understand that, you first have to understand Bologna, because no other city on Earth is so devoted to the idea of portici.
