A certain respect for proportion, which conjoins aesthetics and mathematics, is another chief component of the Tuscan sense of life. You feel it almost anywhere in Tuscany—people seem to pick it up by constant exposure to thoughtful design—but a good place to start is in Pienza, a hill town in the Val d'Orcia and the first truly Renaissance town center in Italy.

I arrive in Pienza with friends, and we decide to have lunch at Sette di Vino, a tiny but excellent osteria. Its owner, Luciano, a wiry, hyperenergetic man and the gadfly of village political councils, regales us with his opera buffa reasons for voting for Silvio Berlusconi, the television magnate and conservative leader; Luciano's performance could be set to music, with a lot sixteenth notes. Then we walk over to the Piazza Piccolomini. Pienza was the brainchild of Enea Silvio Piccolomini, a poet and libertine who, after an adventurous youth of pleasures and disasters, got himself elected pope. As Pius II, he decided to transform this village, his birthplace, into a model miniature city, and around 1459 entrusted the task to a brilliant disciple of Leon Battista Alberti named Bernardo Rossellino. I have never gotten over the magic of this place: Each time I come, I feel that I'm standing in a sort of diminutive Rome that is mercifully free of traffic, an ideal townscape for a pontiff steeped in humanistic studies. The streets meet at right angles, as they might in a metropolis, but bend slightly as they progress outward, preventing one from perceiving how soon they end at the village gates, and the two buildings on either side of the main piazza diverge somewhat, reversing the effect of perspective and appearing to enlarge and define the piazza. It's a triumph of design, but it doesn't end there—it encompasses the entire outlying landscape as well.

I have often had the oddest sense, walking around a Tuscan hill town, that my gaze as I look through the gaps between houses does not stray out toward the horizon amid a loose, discordant smattering of vineyards and hamlets, but is somehow bound to a picture—a picture formed perhaps by a road winding up to a convent, or an alley of poplars flanking the carriageway to a manor. In Pienza, this correspondence between hill town and surrounding countryside is no matter of lucky accident or superimposed desire but was clearly conceived at a stroke. I notice that my vision—channeled through the openings on either side of the duomo, or, later, through the three round-arched doors in the hanging gardens behind the Palazzo Piccolomini—is pinned to specific points on the horizon, such as the fortress of Radicofani, lair of a thirteenth-century gentleman-bandit immortalized by Dante in "Purgatory." The feeling that one has wandered into a painting or stage set, a somewhat fortuitous characteristic of other hill towns like Volterra or Montepulciano, became fully conscious in Rossellino's extraordinary mind.