Kakadu National Park and Litchfield National Park
The Kakadu National Park isn't on the UNESCO World Heritage List for nothing. It's a place of incredible biodiversity which is represented by its indigenous community, the Australian Aborigines, along with fauna including species such as jabiru: this tall, long-necked bird is one of the symbols of the park and one of the towns located inside the park bears its name. The area is also the home of cockatoo, hence "The Kakadu National Park".
Besides cave paintings the park can offer mainly wetlands and lakes which are the natural habitat of saltwater crocodiles, the largest and the most dangerous reptiles in the world. They don't fear people - that's why, during the rainy season when rivers burst their banks, the park becomes very dangerous.
A good place to observe these creatures is the Yellow Water Billabong.
On the way back to Darwin, the administrative center of the Northern Territory, you should definitely make a stop in the Litchfield National Park. Same as in the Kakadu National Park, the best way to explore the land is to stay overnight and enjoy the surrounding untouched nature.