Fosso Bianco (Bagni San Filippo)

Fosso Bianco is a natural hot spring at Bagni San Filippo, in the municipality of Castiglione d'Orcia in Siena province, not far from Monte Amiata. Its waters deposit calcium carbonate, forming white travertine concretions and cascades, most famously the formation known as the 'Balena Bianca' (White Whale). The site's name comes from Saint Philip Benizi, a Servite friar who lived here as a hermit in the 13th century. The grotto and pools are open to visitors free of charge.