Guess where?

Possibly the track up to Cathedral Peak/Bell from the Hotel (the 'last water' in winter)?

@mnt_tiska - sorry, try again

Not sure of the waterfall's name, but that looks like its at Injesuthi.

Old Women Stream near junction M30.

@intrepid - spot on, hoped it would be a trickier one because of being at RNNP which isnt widely hiked.

The hike I did when taking the photo was going up from Mahai campsite, up the Crack gulley, along the ridge looping below Witsieshoek hotel, down Mahai pass, the Waterfall and Mahai cave, and then back to the campsite, fantastic day hike.

I haven't done the homework, but my subjective impression is that Intrepid is taking something of a lead here.
A skill score of successful hits over total guesses might reveal whether I'm right.

Right, I've taken the bait! The scores so far are as follows (correct guesses as a percentage of total guesses):

ST: 3/14 (21%)
intrepid: 12/30 (40%)
mnt_tiska: 1/12 (8%)
ST2: 1/6 (17%)
Magan: 3/4 (75%)
Stijn: 8/19 (42%)
Aux: 0/2 (0%)
ghaznavid: 1/28 (4%)
spook: 0/1 (0%)
jonwells: 1/1 (100%)
buyid: 0/1 (0%)
Sterkhorn: 1/1 (100%)
brio: 1/1 (100%)

Great work Stijn. So on the basis of absolutes Intrepid is well clear at 12 correct. Then there are the hundred percenters who keep their powder dry for the right moment - a neat trio of Sterkhorn, Brio and JonWells. Somehow the most impressive to me is Magan at 3/4. Quite a record to protect. My shameful 8% makes me think I either should have kept the notion of quantifying the tally to myself or that I need to get out more often!