A SHORT WALK from Bordeaux’s celebrated Château Pétrus brings you to a sandy-colored gravel drive, at the end of which stands a small farmhouse. You could be forgiven for thinking it was just a modest family home, albeit surrounded by a vineyard. And you wouldn’t be far wrong. But what might surprise you is that this tiny, 4.5-hectare property produces one of the world’s greatest red wines: Château Lafleur.

Bordeaux has changed a lot since Henri Greloud built the house and cellars in 1872. Drive through the Médoc at night...