There is a famous trek in Borneo not involving (to much) jungle, humidity and leeches, and it is the climb of Mount Kinabalu (4096m).
One problem is that the two days climb is really expensive. You have to pay for the park entrance, the climbing permit, the insurance, the guide and the accommodation. Mark (an English guy who shared my adventures in Borneo) figured out that the accommodation alone was 100 euros for a night in a lousy dormitory including food... We figured out also that it is possible to climb the mountain in one day by starting early in the morning, and that was exactly what we did...
The other problem is that the climb starts at little below 1900m and ends at 4095m, which makes a big big journey up, adding the rarefaction of oxygen due to altitude and an even bigger one down never-ending steps... On that way down, Mark taught me new English swear words to throw at the steps while I was bitting my tongue to diverse the pain from my knees. We ended up knackered, but happy as we were rewarded with the most fantastic view from the top. Very well done us!
I had an amazing journey in Borneo, and again, I wish to come back. Farewell wild Borneo !