Coombsville

Coombsville is easy to miss on a map of Napa Valley -- it doesn't have a town, a famous main street, or a cluster of tasting rooms lining a highway. What it has instead is geology: the AVA sits inside the collapsed remains of an ancient volcanic caldera, a horseshoe-shaped basin ringed by ridges that climb as high as 1,877 feet, just east of the city of Napa.

That caldera shape is the reason Coombsville's vineyards nearly all face west, tucked against the inside of the ring rather than spread across an open valley floor. The soil underneath is Hambright-Rock outcrop and Coombs gravelly loam -- volcanic material broken down over millions of years, thin in places and studded with rock. It isn't the kind of ground that makes farming easy, but it's exactly the kind of poor, well-drained soil that tends to produce concentrated wine.

Coombsville became an AVA in 2011, the 200th in the country and the 18th in Napa County, but growers had been quietly building a reputation here for years before the paperwork caught up. Its position -- inland enough to avoid the coldest of the bay fog, but still funneling in afternoon breezes off San Pablo Bay -- puts it in a kind of sweet spot: warmer and later-clearing than Los Carneros to the south, but noticeably cooler than the city of Napa just a few miles to the west. Fog tends to sit here an hour or two longer than it does in neighboring Oak Knoll, which slows ripening just enough to let flavors develop without racing ahead of acidity.

Cabernet Sauvignon is what most growers plant, and it's what put Coombsville on serious buyers' radar, but the AVA has real range -- Chardonnay, Pinot Noir and Syrah all do well on its cooler, breeze-fed sites. Because so much of Coombsville sits close to Napa city, some of its vineyards are practically suburban, wedged between homes and roads in a way that feels almost incidental to the fact that the ground underneath happens to be extraordinary for growing wine grapes.

It's a young AVA, and a quiet one, without the historic wineries or roadside fame of Oakville or Rutherford. But the same caldera geology that makes Coombsville's landscape distinctive -- rolling, enclosed, ringed by hills -- also makes its wine distinctive: structured, cool-edged Cabernet that doesn't taste like it comes from five minutes outside downtown Napa.

Facts sourced from TTB AVA establishment records; Wikipedia (https://en.wikipedia.org/wiki/Coombsville_AVA)