Prambanan is a Hindu temple complex built around the 8th and 9th centuries A.D., a couple hundred years younger than Borobodur, and quite interesting also.
You're free to wander among the temples at Prambanan, poking into wherever you like. Our guide pointed out the more famous statues, and we explored around a little.
There isn't close to the level of high-pressure souvenir sales as the people at Borobodur.
At Prambanan, there is even a small "train" to take you around the park if you want.
From journal Overcharged But loved It!