Bordeaux. Home to the most famous (and most expensive wines) in the world.
While Merlot is the predominant grape throughout the whole Bordeaux region, Cabernet Sauvignon reigns supreme in Haut Medoc/Medoc.
While the famous Chateaux (Cos d'Estournal, Lynch Bages, Margaux, Leoville Barton etc) get the media attention, there is real value throughout the region, no matter what your price point.