The museum is located at 8 Rue Elzevir inside the former Hôtel de Donon which dates from the 16th century and is itself a quite interesting architectural site. Cognacq-Jay is home to art from the 16th, 17th, and 18th centuries and the collection is utterly fascinating. Spread over four floors and twenty rooms, there are works of many genres here. Porcelains from China, ceramics, jewels - and an impressive variety of period furniture.
There is also an impressive selection of paintings ranging from Rembrandt to Cézanne and Degas. I was particularly drawn to the paintings of Jean-Baptiste Greuze whose realist style broke with the bucolic landscapes and portraits favored by the aristocrats of pre-Revolution France. Greuze's work is infused with the gritty realism and honesty that became one of the pillars of the emerging ideological current which spawned the French Revolution. There are several excellent examples of his work on display here.
And while the museum is in the heart of the tourist-packed confines of the 3rd arrondissement, it has somehow fallen off the circuit of most visited places. You will not have to worry about navigating a crush of fellow travelers here. In-fact, I often found myself completely alone in several salons - almost as though I were on a private self-guided tour. It was great.
Don't miss this under appreciated gem.