Chateau Cos d'Estournel is a Grand Cru vineyard located in Saint-Estèphe. Today it covers 170 acres separated from Chateau Lafite, along the southern edge, by the stream between Saint-Estèphe and Pauillac. The gravelly soil, over a flint, limsetone and silicate subsoil low in nitrogen, has eroded over centuries to form steep ridges which perfectly drain the vineyards. The vineyards are planted 60 percent to Cabernet Sauvignon vines, 2 percent to Cabernet Franc, and 38 percent to Merlot. Naturally, the percentage of Cabernet or Merlot in the composition of each vintage depends on the climate which favours one grape variety or the other.