The Carrousel du Louvre isn't under the museum. It's under the glass pyramid that serves as the entrance, but that's above the museum.

As long as we're being pedantic, that's not right either. The large pyramid that is the entrance is not exactly "above the museum" itself. It is above a lobby and service area that provides direct access to the three wings of the museum, which is itself almost entirely above ground, which means that the pyramid cannot be above the museum.

The Carrousel du Louvre is itself toward the end of those wings, and is underground. It is lit by a second 'inverted" pyramid in the center of the traffic circle that cuts the great courtyard in two. The Carrousel du Louvre is made up of a shopping center, including a food court, and an exhibition center for trade shows, etc. that was conceived from the start as a venue for the fashion shows that stubbornly refuse to leave the tents of the Cour Carrée.

Well, the pyramid is on the same level as a lot of the museum but it's above some of it, I don't think you could claim that "almost all of it is above ground" actually. But point taken. It's above the entrance and some of the lower spaces.

My point though was that the writer here made the carrousel sound like a basement underneath the museum, and that's the wrong picture. As you pointed out, it's not. It's under a traffic circle.

But above the body of Mary Magdalene, right?

We'll never know.