This is the Spanish Villa in the former French Concession where Zhou Enlai lived in 1946. He was the first leader of the the People’s Republic of China, friends with Mao Zedong. The house has been left exactly as he left it, so it's a great museum of that era.
It's a very small fee to get in and well worth the stop if you're strolling in the Concession.
Photo by 猫猫的日记/Wikipedia.