The peninsula is around 200 by 300 kilometers, and is bio-geographically diverse, containing coastal plains to the south. The Arfak Mountains are a 2900-meter-high mountain range that are found in the east. Slightly shorter than the Arfak Mountains, the Tamrau Mountains are found in the north. Bon Irau is the highest mountain in the Tamrau Mountains, at . The highest mountain on the Bird's Head Peninsula is Mount Arfak. It is high and is located 21 miles southwest of Manokwari. Both of the mountain ranges have a diverse mix of sandstone, limestone, and volcanic rock. A large basin called the Kebar Valley divides the two mountain ranges apart.