Bordeaux sucks up all the oxygen, leaving little air for the wines of the Dordogne and Lot valleys. But vintners in both regions have rededicated themselves to quality in recent years, producing world-class wines worthy of far more attention than they receive. We visited three wineries during our stay, in addition to the Château de Mercuès, and discovered delicious bottlings in each. Indeed, top Cahors Malbecs can now compete with some of the finest red wines in the world.