Besides the caves, Mulu is also great for jungle trekking. The more adventurous can trek up to the Mulu Summit, which is a grueling 4 day trek, or the Pinnacles - a 2 day 1 night trek. There are also several easier treks which be done in a few hours. I decided to visit the Paku Waterfall, which is around 6km from the Park HQ and a relatively easy walk. On the way you will pass through pristine jungle filled with wonderful flora and fauna.
I saw many species of wild mushrooms and fungi.
The waterfall is not very big, but beautiful nonetheless. Not many people go there, so you can have it all to yourself.