Tanjung Puting National Park was definitely one of the highlights during my 3.5 month trip to Indonesia. It's a great place to view orangutans - you will see mainly rehabbed animals but we also found some wild ones. Also proboscis monkeys, gibbons, and many bird species. Traveling by klotok (wooden houseboat) makes the whole experience even more special. You sleep on a mat under a mosquito net and sleep to the sounds of the jungle. Our local guide from Kumai, Fardi, was great. He's very knowledgeable about the wildlife and you can tell that this job is his first love. Not the easiest or cheapest place to get to but worth the effort.