The hills south and west of Bologna, in the center of the Region, have always yielded fine wines. Altitudes reach 450 meters above sea level (Monte San Pietro), and the terrains and microclimates vary considerably. There are many PDO wines but if one is interested in the traditional varieties the most important is certainly Pignoletto. This indigenous grape was first mentioned by Pliny the Elder in the Ist Century B.C. as "Pino Lieto, not sweet enough to be good." The 140 companies that belong to the Colli Bolognesi PDO produce around 25,500 hectolitres of wine and 500 hectolitres of Colli Bolognesi Classico Pignoletto. In 2010 this was recognized as the second DOCG* wine in Emilia Romagna, governed by a particularly strict PDO regulation calling for a minimum of 95% of Pignoletto grapes and a minimum alcohol content of 12% vol. *DOCGs are denominations governed by particularly strict PDO regulations.