I found 5 Queen's Avenue, which is a high-grade office building called Hengyi Building. There is no Xu's Art Museum on the map of the building. Ask the staff. Answer - "I've never heard of it. Xu's Hall, the only Chinese among the five largest collectors in the world, is an important part of the Art Museum of the University of Hong Kong. The Hong Kong Museum of Culture also has "Xu Exhibition Hall China Art Museum" free of charge.