There is a walkthrough page on the guide that mentions it I think. It says: Nectary Cellar / Tomb of Isael / Tomb of Jean Necteaux
In order to get inside initially, you'll need to search for the hidden door. The Nectar Research Assistant Needed Adventure must also be pursued to get progressively further in. Look for two hidden doors inside this place. The first is in the room with two large rocks, the second in the hall just before the room with the Nectar bottle you need. The second of these hides the French Signet of the Nectary Cellar. Once you've traveled to Egypt through the adventure chain, the Tomb of Isael will be unlockable via its keystone. Look for it on the pedestal in the center of the room once you're told to re-inspect the three holes.
Plus there's more written there I think. The link is:
http://www.carls-sims-3-guide.com/worldadventures/france/
