See Wild Orangutans
Borneo is one of two places on Earth (Sumatra is the other) where endangered orangutans can still be seen in the wild. Orangutans are among the smartest primates; they make medicine, craft tools, and even exchange gifts. Unfortunately, because of habitat loss caused by massive palm oil plantations, orangutan numbers are dwindling; now is the time to see them while you still can.
The Sepilok Orangutan Rehabilitation Centre in East Sabah is the most popular place to view orangutans in Borneo. A better option is the cheaper and less crowded Semenggoh Wildlife Rehabilitation Centre just outside of Kuching. While there are never guarantees, you have a pretty good chance of seeing semi-wild orangutans at both refuges during feeding times.
Discover the Rainforest
Only open to the public since 2006, the Rainforest Discovery Centre in Sabah is a world-renown environmental education center. For a low entrance fee, visitors can explore a fantastic array of plants, insects, and animals found in Borneo's rainforests. After touring the well-manicured botanical garden and education center, visitors can then apply their new knowledge while trekking along the many trails nearby.
An impressive matrix of canopy walks elevate visitors above the dense trees where they can spot rare birds and sometimes orangutans.
Go Scuba Diving
Not all of Malaysian Borneo's natural attractions are found on land. Sabah boasts some of the world's premier scuba diving sites. Compared to diving in places such as Malaysia's Perhentian Islands, diving in Borneo is indeed not cheap. But since you'll get to see turtles and macro life, along with hammerhead and whale sharks, it's worth the extra money.
The diving in Sipidan is so famous that conservationists only issue 120 permits per day to preserve the fragile reefs; you must organize your diving well in advance to make sure you get a permit.
Mabul, a nearby alternative to Sipidan, offers arguably some of the best muck diving in the world and is also considered the best dive site for underwater macro photography.
Climb Mount Kinabalu
At 13,435 feet tall, Mount Kinabalu in Sabah is the tallest mountain in Malaysia, the third-highest peak in Southeast Asia, and one of the tallest peaks in the region that can be climbed without technical equipment.
Reaching the summit of Mount Kinabalu requires only the stamina and heart to do so. About 40,000 people per year come to try the grueling, two-day ascent; many don't make it to the top. The last part of the climb requires a rope-assisted scramble through the clouds to the peak.
Aside from one impressive mountain, the 300-square-mile Kinabalu National Park has a mind-boggling amount of flora and fauna. Meeting international biologists and botanists who have come to study the estimated 4,500 plant species is an everyday occurrence on the trails.
See Exotic Wildlife on the Kinabatangan River
Although the name is a mouthful, the Kinabatangan River area in Sabah is often the favorite highlight for visitors to Malaysian Borneo. Lodges along the tiny, single-path village of Sukau offer accommodations and guides who take people up the muddy river by small boat. A quiet approach by boat allows visitors the opportunity to spot highly endangered proboscis monkeys, orangutans, crocodiles, pythons, and elephants when they are in season.
Chill on a Beach or Island
Malaysian Borneo is not at all just about sweating and swatting insects in the jungle. Miles of pristine and wild beaches will give you plenty of opportunities to unwind after a few days of trekking.
Tiny Mamutik Island in the Tunku Abdul Rahman Marine Park—only 20 minutes by boat from Kota Kinabalu—allows camping directly on the beach. Alternatively, check out Tanjung Aru, more of a local's beach scene with very few tourists, just a few minutes south of Kota Kinabalu.
If you need some island time, check out the different vibe on Labuan Island, an enjoyable, duty-free island off the coast of Sabah. "Survivor" fans should get to remote Pulau Tiga where the first season of the hit show was filmed.
Stay in a Longhouse
Visitors to Sarawak can visit and stay in an Iban longhouse to see how indigenous people live. While some longhouses are strictly tourist experiences, it is possible to see authentic ones only accessible by river and far removed from city life. You'll get to sample authentic food, see a traditional dance performance, and learn to shoot a blowpipe gun just for fun.