The Elsa river is in the Italian region of Tuscany. It rises from its source at Montagnola Senese and flows northward to empty into the left bank of the Arno. From its source at Molli, Sovicelle, the flow of the river is low until its reaches its major tributaries at Vene di Onci and Caldane. Its total length is 63km. It passes the towns of Colle di Val d’Elsa, Poggibonsi, Certaldo, and Castelfiorentino. See Val d’Elsa.