OMBRONE, river in Tuscany which flows into the Tyrrhenian Sea (western Mediterranean). It rises in the township of Castelnuovo Berardenga in the south of the Chianti Classico DOCG. Its tributaries are the Arbia, (just south of Buonconvento), the Merse, and finally the Orcia (see Orcia DOC) on the south-western edge of the Montalcino region.