Keraton Ratu Boko in Yogyakarta. Keraton means palace.
Ratu Boko or Boko temple (Javanese: Candhi Ratu Baka) is an archaeological site which is a complex number of the rest of the building which is located approximately 3 km south of the Prambanan complex, 18 km east of Yogyakarta or 50 km southwest of the City Surakarta, Central Java, Indonesia. Ratu Boko is situated on a hill at an altitude of 196 meters above sea level. The area of the whole complex is about 25 ha. 
This site displays the attributes as a place of activities or settlement sites, but their exact function is not clear.  Ratu Boko estimated to be the one in the 8th century during the Sailendra (Panangkaran) of the Kingdom Medang (Mataram Hindu). Considering from the pattern of the layout of the remains of the building, allegedly this site is the former palace (royal palace). This opinion is based on the fact that the complex is not a temple or building with a religious nature, but rather a fortified castle with evidence of the rest of the fort wall and dry moat as a defense structure.  Remnants settlements were also found in the vicinity of this site.
The name “Queen Baka” is derived from local legend. Ratu Baka (Javanese, literal meaning: “the king of stork”) is the father of Loro Jonggrang, which also became the name of the main temple at Prambanan temple complex. This building complex is associated with the legend Loro Jonggrang of the local people. 
Administratively, the site is located in the region of two of village , namely village Dawung, Bokoharjo Village and Hamlet Sumberwatu, Sambireja village, Prambanan subdistrict, Sleman, Yogyakarta, Indonesia.
The site is to be nominated to the UNESCO World Heritage Site since 1995.
source : Wikipedia.