The lovely Art Deco building that houses the Teien Museum was completed in 1933, with interiors designed by Henri Rapin and decorative glass work by Rene Lalique. The beautifully decorated and well-preserved rooms serve as a unique backdrop for the museum's exhibitions, and the Japanese-style garden and teahouse behind the main building are a nice bonus attraction.
The themes for the exhibitions vary quite a bit, so it might be worth waiting for something of special interest to come around. Recent exhibitions have been devoted to Art Deco architecture, French picture books, Meiji-era Cloisonne, the gems and jewelry of the Medici, and wooden benches made by indigenous peoples of Brazil.
There are two separate museum shops - called Blanc and Noir - and the one at the museum's front entrance (Blanc) is worth checking out even if you're just passing by, especially if you're looking for tasteful design-conscious gifts or souvenirs. There's also a pleasant museum cafe which looks out onto the garden area and serves luxurious desserts.