The winemaking tradition of Lombardy dates back to its settlement by Greeks from Athens along the Po River. Today, Lombardy is considered the industrial and commercial capital of Italy and the gateway to Europe. The region annually produces over 125 million litres of wine. Lombardy is well-known for its sparkling wines made in the Franciacorta and Oltrepò Pavese areas. The Valtellina zone produces many notable wines using a local version of the Nebbiolo variety. The stony soil composition of the region helps to retain heat that is released during the evening to warm the vines. While the weather of Lombardy is varied, the region is generally considered a cool continental climate and is influenced by several geographic features that control the temperature and terroir of the land. These include the Alps located in the northern parts of the region near the wine producing area of Valtellina and the Po River, which runs along the Oltrepò Pavese and forms most of the region's southern border with Emilia-Romagna. Many wine areas are located near some of Lombardy's major lakes, including Franciacorta near Lake Iseo as well as the Garda Bresciano and Garda Mantovano regions near Lake Garda. To the west of Lombardy is the Piedmont wine region, to the south is Emilia-Romagna and to the east are the Trentino-Alto Adige/Südtirol and Veneto wine regions.