Central Javanese ("Jawa Tengahan") is founded on the speech of Surakarta and to a lesser extent of Yogyakarta. It is considered the most "refined" of the regional variants, and serves as a model for the standard language. Those two cities are the seats of four Javanese principalities (heirs to the Mataram Sultanate) that once dominated the whole of Java and beyond. This variant is used throughout Central Java and Special Region of Yogyakarta, and there are many lower-level dialects such as "Muria" and "Semarangan", as well as "Surakarta" and "Yogyakarta" themselves. The variations in Central Java are said to be so plentiful that almost every administrative region (or "kabupatèn") has its own local slang; but those minor dialects are not seen as distinct by most Javanese speakers.