The Sonobudoyo museum is located on the north side of the North Square of Sultan's Palace. It was built in 1935 according to Javanese architecture. The architecture of gateway resembles to the entrance of the mosque in Kudus in the way to the auditorium and main joglo structure which are connected, while Kudus is the most ancient town in the island of Java beside Kotagede. The museum has the second most complete collection of cultural artifacts after the central museum in Jakarta, like ceramic from the Neolithic Age, statues and bronze articles from the 8th, 9th and 10th century originating from the temples of Central Java, various kinds of masks and wayang (puppet for shadow play ), a gamelan or orchestra, an ancient weapon collection, heir looms and artifacts from Bali. This museum is also an interesting library that keeps various ancient books related to the Javanese culture.
source by http://www.jogjatourism.com/html/senobudoyo.htm