Well Pale Horse asked about one of my favorite AVA (American Vitacultural Area, much like the AOC, DOC, GI, etc etc) Napa Valley, America's greatest wine making region, and the first truley great wine region in the "new world" has 14 sub regions, or AVA's in it.
Spring Mountain is one of them. It is the Steepest and wettest (although still allmost bone dry by other countires definations of rain fall). It gets its name for the many natural springs that are found in it. It is loacted from 600 to 2,600 feet above sea level in the Mayacamas Mountain range. it is a mixture of Volcanic and Sedimentery soils, which gives way to red wines that have deep color, a lot of soft tannin, lower acidity (highwer Ph), fat rich flavors. Whites can be fat to lean depending on the soils they are planted in. Originally know for their whites, this has changed int he past 20 years to one of the best areas for red wines in Napa. With Wineries like Pride, Barnett, Fisher, Cain, Marston, it is easy to see why.