Hidden behind the popular Kota Tinggi waterfall lays its source, Gunung Muntahak. This 634m hill is relatively unlogged and large area of its primary rainforest still remains intact and undisturbed by human intrusion. From the main road leading to Kota Tinggi waterfall, it is not possible to see this hill as it is well hidden by other smaller hills. The dim interior and rich humus cover provides an ideal condition for the growth of a rare and beautiful palm, Johannesteijsmannia altifrons (Common name: Joey palm, diamond joey). This plant has leaves that can easily stretch over a storey high for matured specimens.
The initial part of the trek is actually more interesting as it passes through an old tin mining land. Orchids and pitcher plants grow in abundance in this nutrient poor ground. Although the water bodies in the land was the result of rain water collected in the mining depression, the last and the largest one before entering the forest is beautiful with an aura of peaceful tranquility. Far from being devoid of life, the pond contains many fishes and frogs. The flat land beside the pond makes this place suitable as a campsite although it is not advisable to use the water in the pond for drinking. Standing at the edge of the pond, a loud shout would be rewarded with a clear echo.