From Wikipedia: http://en.wikipedia.org/wiki/Serchio
Serchio (in antiquity the Auser) is the third longest river in the Italian region of Tuscany at 126 kilometres, coming after the Arno (242 km) and the Ombrone (161 km). By mean rate of flow, it is the second largest, smaller than Arno but larger than Ombrone. The principal source forms on the slopes of Monte Sillano (1,864 metres) and is joined by a secondary branch, the Serchio di Gramolazzo, at Piazza al Serchio.
The Tuscany, one of the most beautiful Italian regions, is known throughout the world for its Landscapes and for the Works of Art that it houses (It is the birthplace of the Italian Renaissance). Six localities have been designated World Heritage Sites: the Historical Center of Florence, Siena, San Gimignano and Pienza, the Square of the Cathedral of Pisa with the Leaning Tower and the Val d'Orcia. It is in the central Italy and borders with Emilia Romagna (north), Marche and Umbria (east) and Lazio (South). The West coast is bathed from the Ligurian and Tyrrhenian Sea; here we can find the islands of the Tuscan archipelago including the island of Elba. The regional capital is Florence and the other provinces are: Arezzo, Grosseto, Livorno, Lucca, Massa, Pisa, Pistoia, Prato and Siena.