"The Louvre’s Secret Apartments"

We've looked at a few secret apartments over the years, some links below.
From Messy Nessy Chic:

The Louvre; or, as we’ve prefer to call it, Paris’ most exhaustingly gorgeous tourist trap. In the MessyNessy guide, Don’t Be a Tourist in Paris, there’s even a chapter called, “Anything but the Louvre” that steers folks away from its selfie-stick jungles, and into the arms of more overlooked museums in the city. But this weekend, we decided to pay a visit to the Louvre. Our self-inflicted challenge? Finding a way to visit the museum without “being a tourist”; as it turns out, there’s an entire wing that’s escaped our radar over the years: Napoleon III’s apartments. They’re ghostly, gilded, and a veritable mini-Versailles…

The apartments are hidden in the Richelieu Wing, and if finding them sounds intimidating, fret not; we’re here to guide you into the belly of the beast. You can try your chances at the normal queue by the pyramid, but we suggest sliding in through the Galérie du Carrousel (an underground mall that connects to the Louvre) by the arch, or through the entrance on rue de Rivoli. Once you’re in, make your way to the museum’s hub, which has escalators crawling up to different galleries (i.e. Denon, Sully). You want to aim for “Richelieu.” From there, it’s a straight shot into exploring the luxurious interiors…MUCH MORE

The rooms are very French:

Previously: 
The Apartment Inside Grand Central Terminal
Radio City Music Hall's Secret Apartment

There are more, we'll get to them.