The fort is encircled by a combination of four earthen ramparts and ditches, though there is some suggestion that stone walls may have played a minor part in the defences of the fort (unlike White Caterthun, where the defensive walls are almost entirely of stone). There are four earthen banks and ditches.
The innermost bank is in very poor condition and encloses an area of about 200 by 260 feet. This inner bank is surrounded by a much more solid and impressive bank, into which nine entrances have been cut. There are two further banks, with a large number of entrances.
Visiting Brown Caterthun
Of the two Caterthuns, Brown is the more impressive to archaeologists, due to the complexity of the earthwork structure and the sheer scale of the site. However, from the perspective of an ordinary visitor, Brown Caterthun is difficult to get a lot out of; the earthwork rings are easy to pick out, but from on the ground they are not terribly imposing. And the fact that there are no obvious stone remains means that it isn't an incredibly impressive site to experience.
That's not meant to discourage you from visiting; on the contrary, it is really interesting to visit first one, then the other Caterthun and see the differences between the two sites. Also, from the slopes of Brown Caterthun it is easy to see across to White Caterthun and really get a chance to appreciate the size and scale of the stone rings.
There is a parking area on the saddle between the two Caterthuns, where you will find a useful information panel. From the parking area, it takes about 15 minutes to climb up Brown Caterthun, and waterproof footwear is a good idea because the ground can get wet and muddy. Do take the time to climb White Caterthun as well; its only about five minutes and you get excellent views.
