Sharing the borders with the Sultanate of Brunei Darussalam and the Malaysian stated of Sarawak and Sabah, Kalimantan occupies two-thirds of Borneo, the world's third largest island ( after Greenland and New Guinea ). It is the land of the Dayak people who long ago were famous as courageous warriors. Over 200 tribes live in the island, but most well-known groups are the Kenyah and Kayan in the east, the Ngaju in the central region, and the Iban in the west. Kalimantan, with an area 540,00 km2, represents nearly 30% of the nation's land area, but with less than 5% of the population. The centre of Kalimantan is made up of mountain ranges, whose summits rarely top 1,500 metres above sea level. Great rivers flow down from the highlands, and are often navigable for hundred of kilometres, serving as essential channels of communication between the coast and the island's interior. Travel down the Mahakam and Kahayan River into the Dayak country. On the southeast coast of Kalimantan, Banjarmasin is a busy trading city crisscrossing with many waterways fed by the Barito River. Down-stream on the Barito, you will reach Kaget and Kembang Islands, home of Kalimantan's unusual primate, the proboscis monkey and a variety of birds. Like other ethnic groups in Indonesia, the Dayaks have traditions, such as Manjat Tana, a ceremony requesting land productiveness before opening a new farming area; Pandau, for blessing from the Gods; Bungan Panyelong, Bunut and the Hudog Dance which are performed to ask for rain or thank the Gods after a good crop. In South Central Kalimantan, the Kaharingan religion of several of the more traditional and remote Dayaks is still practised. The tiwah or funerary ceremony is a spectacular series of rites that involve cleaning the bones of dead for their smooth journey to heaven, and animal sacrifices that ensure wealth and good health for the living. The impenetrable, tropical lowland rainforest of Kalimantan hold a diverse variety of exotic flora and fauna; 600 species of birds ( including the hornbills that sacred to the Dayaks ), orangutans, proboscis monkey, clouded leopard, leaf monkey, crab eating macaques and ant-eating pangolins. Tanjung Putting National Park and its three camos, Tanjung Harapan, Pondok Tanggul and Camp Leakey are where tamed orangutans are rehabilitated and taught to readapt to their natural environment. In the Makassar Strait between Borneo and Sulawesi, the tiny archipelago of Derawan, Sangalaki and Maratua shelters a diverse ecosystem that creates a paradise for divers. Surrounded by a shallow lagoon and the reefs, Maratua and Sangalaki present over 500 species of hard and soft corals, manta rays and turtles. The area is also the site of bountiful pearl diving. Kijing and Temajoh Islands in West Kalimantan are also ideal for diving, fishing and sailing.