Yes, that’s me waving wildly.
White Castle is not really a castle in the accepted sense of the word — it is a motte that dates from the early bronze age, if the placard is to be believed. The foundations and remains date from 400 BC or earlier.
A motte is simply a hill, and was one of the earliest forms of fortification. This particular hilltop is terraced, and appears to be at least partly manmade (see Duffus Castle for an example of a failed man-made mound) so that it is easily defended by wooden palisade walls and a few men. Many castles are of the motte-and-bailey type: a mounded hill with a wooden or stone tower, with a large area enclosed by a castle wall. I don’t believe that this motte was heavily fortified, although there are supposed to be foundations of huts and postholes on the top of the hill. Wooden walls would be long gone, of course, leaving only faint traces behind.
The ground is squishy even at the top of the motte. It feels waterlogged, spongy. It’s strange to walk on, like walking on pillows; you are constantly feeling as if you’ll sink in to your knees.
We nearly missed this interesting site. If it hadn’t been marked on the map as a castle, we probably would have driven right by without seeing anything but a strangely-shaped hill. It certainly seems a strange place to have a fortification.