This is a lovely circle on Knockadoon, I don’t think you are technically allowed on the land by the farm owner but it is sometimes open as part of tours.
Circle K, the largest circle on Knockadoon, is located 100m northwest of Circle J. It has an overall diameter of 31m and is made up of two concentric rings (1.2m apart) of more or less adjoining stones. The tallest stone is 1.2m high, but many are much smaller. The entrance is located in the east, and excavation revealed rock-cut postholes that probably held the jambs of a wooden gate of some sort. The presence of a gate suggests that the rings were only part of the original enclosing structure, for one could easily enter it by stepping over the orthostats. These stones may actually have been the inner and outer linings of a taller earthen bank. In the center of the enclosure was a rectangular building, outlined by rock-cut postholes (Figure 4). These features suggest that Circle K may have been a
domestic ring fort, not a ritual stone circle. The pottery found here dates the site to the late Neolithic/early Bronze Age (O’Kelly 1985).
Taken from nd.edu/~ikuijt/Ireland/Sites/cnoetzel/overview.htm#carraig