Wormy Hillock is the name of the natural mound here. The henge itself is to the SSE of the mound and is 13.5m in diameter, with the oval inside the ditch approximately 6m in diameter. For more details see the Canmore record:
I parked at first track after Orditeach on the A941 and walked north hoping to find the Chapel cairn as well, sadly I didn't and became lost instead. Now looking at a map (which I'd stupidly left in the car) I found I climbed the Hill of Oldmerdrum, down the other side and waded the Kirkney Water to get back onto the main forestry track. Good fun this if somewhat tiring. I doubled back to the bridge, found the wee car park complete with henge and hillock.
I've always wanted to come to this place. It certainly has superb views of Noth. The maze of roads offer superb walks. Take an OS map, helps a lot.
3 miles south of Huntly turn right onto single track road to Mytice. Keep driving until you run out of road then walk for 2 miles on main forestry track. The henge is on the right before you cross the bridge.
Bit of a hike but it's a very peaceful place and you get good views of the Tap o' Noth too.
"The old road that ran through this area was known as 'Wormy Howe' because it was created by a giant worm as it set out to do battle with a rival near Bennachie. Worms or wurms are a type of dragon found folklorically in Scotland, Northern England and Scandinavia; they are hugh serpents lacking legs and wings, but otherwise well equipped with traditional draconic attributes such as jaws filled with razor sharp teeth, poisonous or fiery breath, and avoracious appetite for human flesh. Sadly the legend doesn't say if the two worms met, or what happened when they did. Presumably the shape of the henge prompted the belief that the worm had coiled up to have a nap here.'
"In [Finglenny] there is a 'mound' known as the Wormie Hillock, which has long been regarded as one of the interesting sights of the place. Legend tells us it is the grave-mound of a dragon, which at one time infested the neighbourhood, and was slain at this spot by some unknown St. George."
From 'Place Names in Strathbogie, with notes historical, antiquarian and descriptive', by James MacDonald (1891).