Wild Horse Valley AVA is the smallest and least well-known appellation in the Napa Valley. Though it has been an official AVA since 1988, its location on the eastern border of Napa County due east of Coombsville makes it very off the beaten track for wine tourism and almost everything else. Compounding confusion about the AVA is that parts of it lie in Solano County. Due to its elevation and proximity to San Pablo Bay, it is Napa Valley’s coolest AVA. Some of its land is as high as 2,130 feet above sea level. Of the 3,300 acres within the appellation, about 70 acres are planted to vineyards. Chardonnay and Pinot Noir are the principal grapes here. Lake Heron Vineyard and Winery, which produces Olivia Brion wines, is one of the few producers located here.