One of the major national parks in NT, Kakadu is one of the largest in the territory. Known for its rock art, and intact unique biosphere, it is also one of the only two parks in NT which charges an entry fee (exorbitant in my opinion).
Here is a sampling of the rock art that can be seen in numerous areas throughout the park. Indigenous peoples have been using these areas for thousands of years. In many, there are successive layers of rock paintings overlapping each other going back as far as 15,000 years.
The views are pretty good too.