The small carpark area.
It's RM1 per person per entry. It's very cheap and you don't have to pay for carpark or bathroom facilities. You can picnic there as they provide wooden tables and chairs for people to hang out and eat.
Then to see the waterfall above, you'll have to climb quite many steep stairs. It's tiring okay -.-' but it'll take around 15 minutes or so only. After climbing the stairs at Telaga Tujuh in Langkawi and this, I think I'm in a training to climb Batu Caves already *laughs* You'll then reach the waterfall and you can bathe there, play water and what not. I mean I have seen better waterfalls but it's still nice. Water is cold and clear and air is clean =) Suitable for outdoorsy people!
My only complaint; bathroom is filthy!! It makes you think twice whether to change there! And the driving road leading to the waterfall is freaking one way!! We were silently praying no one is heading down when we were heading up -.- If not, park down there and walk 2km to reach Sungai Gabai and then if you want to see the above waterfall, you'll have to walk on steep stairs. By the time you reach *faints* However, it's very good exercise LOL
And lastly, always go with good company! The place is only as much fun as the people you're with!