A beautiful national park with amazing views. I stayed in a hostel that was entirely bamboo huts on the river, possibly the most picturesque accomodation of the trip (Green Bamboo Lodge). The food was also amazing, all cooked in house (I'd recommend the Pork Clay Pot - this might be a bad translation but it's literally pork in a clay pot), and of course there was cheap beer.
You can get a boat across the river to the National Park, where you can take a hike through the jungle on your own or with a guide. I got a bit lost, but as long as you stay on the path you can't really go badly wrong.
There's also a monkey sanctuary nearby, which we were guided round by some local teens. You can see monkeys around the whole park but they can be hard to spot, so I'd recommend this sanctuary as they do some conservation work.