Almost every building in Assisi is roofed with the same terra cotta tiles, which I can't stop photographing. They range from oyster to the near-black of moist earth; some drift through muted versions of reds and oranges. The lines are geometric and the colors are scattered all over the roofs in no pattern. Most of these roofs are centuries old, so the tiles have faded, chipped, grown moss. They're perfect in any light, an entire graduate course in pattern and variation, in the breathtaking beauty of staying within limits and ringing the infinite possible changes. Which, of course, is the challenge and the thrill at the heart of genre writing.