The valley owes its shape to a bank of marine clay laid down when the Pliocene sea covered southern Tuscany. That clay produces the crete — bare, pale, eroded slopes that farmers spent eight centuries trying to plant. Siena's medieval republic bought the land outright in the fourteenth century, drained the marshes and settled tenants along the Via Francigena, the pilgrim road from Canterbury to Rome. The result was agricultural policy that accidentally became landscape design. UNESCO inscribed the Val d'Orcia as a World Heritage cultural landscape in 2004, citing it as an image absorbed into Renaissance painting and, through that painting, into the European idea of good government itself. Ambrogio Lorenzetti's frescoes in Siena's Palazzo Pubblico show these hills as the visible proof of civic order. The cypress avenues so heavily photographed today are mostly nineteenth-century plantings along farm drives, but the ridge-line towns are older. Pienza was rebuilt from 1459 by Pope Pius II, who razed his birth village of Corsignano and commissioned Bernardo Rossellino to raise the first planned Renaissance town in Europe — a trapezoidal piazza, a travertine cathedral aligned to the winter light, and a palace loggia opening onto Monte Amiata. Montalcino sits on a limestone spur to the west, its Brunello vineyards codified as Italy's first DOCG in 1980. Montepulciano, east across the Chiana watershed, holds Vino Nobile and Antonio da Sangallo the Elder's Tempio di San Biagio, a Greek-cross church of honey travertine standing alone below the walls. Between them lie Bagno Vignoni, whose central piazza is a Roman thermal pool rather than a square, and the Abbey of Sant'Antimo, a French-Romanesque church in alabaster founded by tradition under Charlemagne. Any val d orcia day trip from florence crosses roughly 120 kilometres of this terrain, tracing the Orcia river past Rocca d'Orcia and the Amiata volcano. The region matters now for reasons its planners never intended. It is a rare working agricultural landscape protected in its entirety — pecorino di Pienza, Sangiovese Grosso, saffron and cinta senese pork are produced within the same boundaries that guarantee the view. Access to the valley itself is free, at 0 EUR, though individual sites may charge. Operators running a val d orcia day trip from florence tour tend to pair one wine town with one architectural town, which is how most Tuscan hill towns wine tour itineraries are built. The valley rewards that pairing: it was never scenery alone, but land under continuous cultivation, held in shape by the same hands for eight hundred years.