Looming above the town of Borja and its 5,000 residents, Moncayo stands more than 7,000 feet high, the tallest mountain in the Sistema Ibérico range that runs from Rioja to Valencia. Snow covers its three peaks from October to May. Unlike most of the mountains in the range, it is composed primarily of granite, which crumbles to slate on the surface as the weather pounds it down over millennia. If you pull off the highway and drive up the dirt roads into the hills, you'll discover hidden parcels of Garnacha vines, some more than a century old. Wine Spectator's Mitch Frank explains.