Prambanan poses a restoration problem that most ruined monuments do not, and the answer adopted has shaped what stands there.
A Shaiva monument beside a Buddhist one
The Shivagrha inscription of 856 records the dedication, with construction begun under Rakai Pikatan. Three main shrines stand for Shiva, Vishnu and Brahma, Shiva's tallest at forty-seven metres, and the galleries carry the Ramayana in relief.
The useful fact about Prambanan is its neighbour. Borobudur, a Buddhist monument, was built a short distance away and only a few decades earlier, by related dynasties in the same small area of central Java. Two of the greatest religious monuments in Southeast Asia, of different religions, near-contemporary, within sight of the same volcano.
Whatever the relationship between the Sailendra and Sanjaya lines was, and it is argued over, it was not one in which either religion had the field to itself.
Abandonment
The site was abandoned within about a century, probably in connection with an eruption of Merapi and the shift of the Mataram capital to eastern Java. Earthquakes brought the towers down, and they lay as heaps of numbered rubble for centuries.
The rule
Reconstruction began under the Dutch in 1918 and continues. The governing rule is anastylosis: a building may be reassembled only from its own original material, with new material limited to what is structurally unavoidable.
The consequence is visible everywhere on the site. The Shiva temple was completed in 1953 and Vishnu in 1991. Where too few original stones survive, the temple is left as its foundation, a bare stone platform, deliberately not rebuilt.
Dozens of the subsidiary shrines are in exactly that state. A visitor walks through a field of empty plinths, and each one is a decision not to guess.
Set against Bagan, where reconstruction under the Myanmar military invented architectural forms that had never existed and cost the site its UNESCO standing for decades, the discipline at Prambanan is the argument for restraint made in stone.
In use again
A state tourism corporation manages the complex rather than a religious body. But Balinese and Javanese Hindus have reclaimed it for ceremonial use since the 1990s, and Galungan and Nyepi observances are now held there, so the reconstruction has, incidentally, produced a working temple.