There are definitely places to eat inside the Louvre. If you went years ago, before they opened up the actual Medieval Castle (found upon excavation for the Pyramid), it is one of the most amazing parts of the museum, which is saying a lot.
So much of it is preserved. As years went by, the moat silted in, the banks of the Seine were raised again flooding, slowly the Castle itself disappeared. But you can walk through it, look into the water wells that were used to supply the Castle, and see much of its ramparts (the upper part is mostly gone, as you look up, it disappears into the ceiling of the ground floor of the main Louvre, above). Near it is an exhibit of the history of the Louvre.