The Medang kingdom or the Mataram kingdom was a Javanese Hindu-Buddhist kingdom which flourished between the 8th and 11th centuries. It was based in Central Java, and then in East Java. The first account of the Medang Mataram Kingdom is in the Canggal inscription, dated 732, discovered in the Gunung Wukir Temple compound in the village of Canggal, southwest of the town of Magelang. This inscription, written in Sanskrit using the Pallava script, tells of the erection of a lingga (symbol of Shiva) on a hill in the Kunjarakunja district , located on a noble island called Yawadwipa (Java), blessed with abundance of rice and gold. The lingga was founded by order of Rakai Mataram Sang Ratu Sanjaya (King Sanjaya Lord of Mataram) the founder of the kingdom. At its peak, the kingdom had become a dominant empire—not only in Java, but also in Sumatra, Bali, southern Thailand, Indianized kingdoms of the Philippines, and the Khmer in Cambodia.
This episode is also available as a blog post: http://martinifisher.com/2020/06/26/the-golden-age-of-java/