Our disorganized guide gave Old Vine Family Cellar in Kvareli, Georgia, only about 15 minutes’ notice of our arrival. We walked into the garden, past a sheep grazing amid a neighbor’s beehives, and discovered a single massive grapevine, which created a canopy over the patio. Giorgi, the owner and winemaker, told us that the vine was more than 100 years old and that no one could figure out its variety. He still makes a small amount of wine from its grapes each year.