With Malaysia's five highest mountains and two longest rivers, Borneo is a paradise for adventure travelers.
The island is shared by three countries (Malaysia and Brunei in the north and Indonesia in the south). The Malaysian portion of the island is divided into two states: Sabah to the east and Sarawak to the west. (Brunei is on the northern coast, bordered by Sarawak and the South China Sea.) Flights to Borneo are less than two hours from Kuala Lumpur, and travelers can fly directly into Sabah's capital, Kota Kinabalu, or Sarawak's capital of Kuching.
In Sabah, travelers should start with the Kinabatangan River, the second-longest river in Malaysia. Kinabatangan is known for its wildlife, limestone caves and mangrove swamps.
Wildlife safaris are popular along the river, where travelers will be able to see crocodiles, orangutans, elephants and proboscis monkeys, a species that can only be found in Borneo.
Along the river, about 40 miles from Sabah's second-largest town, Sandakan Town, travelers will find the Gomantong Caves, which is the biggest cave system in Sabah.
Simud Hitam, or Black Cave, is the more accessible of the two caves, but if it is a challenge you are after, try for Simud Putih, or White Cave. This secluded spot requires a certain level of caving experience and gear, as it is only accessible after a steep, 30-minute climb into the mountains.
Sabah is also home to some of the top diving spots in the world. Popular animals to spot are green and hawksbill turtles as well as dolphins, barracuda, parrotfish, eagle rays and whale sharks.
Adventurers will want to begin their trip through Sarawak at Lambir Hills National Park. Terrain is varied, so hikers of all levels can find something to enjoy. More advanced hikers will want to trek to the summit of Bukit Lambir, which is the highest peak in the 17,000-acre park.
Sarawak's true claim to fame is the Gunung Mulu National Park, a Unesco World Heritage Site that is home to the Mulu Caves, one of the longest networks in the world. The Sarawak Chamber is the world's largest underground cave, capable of holding 40 Boeing 747s, while Deer Cave is the world's biggest cave passage; it could fit five structures the size of London's St. Paul's Cathedral.
The best way to see the adventurous side of Malaysian Borneo is with an experienced guide. For luxury travelers, consider Remote Lands, a bespoke service for FIT travel that can tailor individual itineraries based on level of adventuring experience.
Another option is Asian Overland, a Kuala Lumpur-based agency that specializes in all areas of Malaysia.
Their itineraries cover wildlife trails in Sabah and Sarawak as well as soft adventure and encounters with some of Borneo's local tribes.