Candi Sambisari is a Shiva temple and possibly the latest temple at Prambanan to be erected by the Mataram dynasty. It was discovered by a farmer in 1966. Excavated from under ancient layers of protective volcanic ash and dust, it lies almost 6m below the surface of the surrounding fields and is remarkable for its perfectly preserved state. The inner sanctum of the temple is dominated by a large lingam and yoni (stylised penis and vagina), typical of Shiva temples.
It's about 2.5km north of the main highway just past the airport, reached via a country lane.