The most visually impressive and romantic area of Tuscany is the Val D’Orcia: the valley of the Orcia River. It was declared a UNESCO World Heritage Site, and your first glance will tell you why. For millennia man has worked this hilly land turning it into a vast, sensuous, harmonious paradise. If there was ever a perfect symbiosis between man and nature, this is it. Best to have a bottle of wine with you and stop often.
From Pienza, head south then turn left to village of Montechiello, one of Tuscany’s most stunning, miniature worlds (all of it 600 years old and delicately restored). Double back toward Pienza, but turn south to Radicofani to stuff yourself with lunch at La Grotta. Then continue to Bagno San Filipo and soak under hot cascades of the thermal baths. You’ll be enormously relaxed as you head on to Castiglione d’Orcia, with its spectacular views from the tower, then on to San Querico and Pienza. Do visit every town. This is a long day trip; if you want to break it up, every town I mentioned is perfect for an overnighter.