Oyo River

The Oyo River is a river in southern Central Java and Yogyakarta, in the central south area of Java island, Indonesia. It is a tributary of the Opak River.

It was the river on which the historical palaces of Mataram were located - Sultan Agung's Karta palace, and his son's Plered palace.

Geography
The river flows in the southwest area of Java with predominantly tropical monsoon climate (designated as Am in the Köppen-Geiger climate classification). The annual average temperature in the area is 23 °C. The warmest month is October, when the average temperature is around 24 °C, and the coldest is January, at 22 °C. The average annual rainfall is 2970 mm. The wettest month is January, with an average of 537 mm rainfall, and the driest is September, with 22 mm rainfall.