Bani Awf (or Bani Auf) is a wadi that links Rustaq to Nizwa. The road in this wadi is really made for 4WD cars : some part of the tracks are flooded and you need an elevated car to go on. also at the end of the track it goes very (very) steep.
The main point of interest of this track will be the "Snake canyon", which is 300 meters deep, where you can go canyoning or via ferrata but better to have a guide to do these dangerous activities, moreover you need a specific equipment.
There is also the "little" Snake Canyon which is more accessible where you can walk and swim in
You will cross 3 or 4 small villages. The Palm trees of these villages will make a good spot for picnic or camping.
Note : you can do this wadi yourself referring to wadi bani awf in the Oman off-road explorer guide