Northern Rockhole, in Nitmiluk National Park (Katherine Gorge), is an enjoyable half day walk from the Nitmiluk Visitor Centre at Katherine Gorge.
It's also a lovely lunch spot on the first day of the iconic Jatbula Trail. You'll climb over dark volcanic rocks to reach the base of the falls, where you can see many layers of sedimentary rocks in the cliff face. A lovely swimming spot, in the early half of the year, is usually a single drop waterfall that you can bathe beneath. As it starts to dry out, the smooth green pool provides unusual 'must see' reflections.
You can do the return walk from the Nitmiluk Visitors Centre to Northern Rockhole in a day. Walkers must register at the Nitmiluk Visitor Centre and will need to book a short Ferry ride to cross the Katherine River – You can book this at the Visitors Centre.