There are nine broch and possible broch sites in the Dunbeath area. The only one to be excavated is Dun Beath itself. The name could have been dun beithe - 'the height or fort of the birches', or it might have meant 'the height or fort of Beath, Beth' or some similar personal name. It stands on the promontory formed by the confluence of the Houstry Burn with the Water of Dunbeath. The site was dug by the landowner, Mr W S Thomson Sinclair, younger, of Dunbeath, in 1866; before excavation it appeared as a large mound or cairn. He removed most of the stone from the site, so that there is no longer any evidence of possible extra-mural structures around the broch, apart from faint traces of a wall to the SE. The excavator may also have carried out some 'repairs' in the interior. A wall was also built around the broch after the excavation, actually cutting across the foundations in the southern arc, making access for inspection and photography very difficult.
The interior measures just over 8m in diameter and the enclosure wall is 4.3m thick at the entrance. The entrance passage is in the SE, 4.3m long and about 1m wide at the entrance. About 1.2m in from the entrance the passage widens to about 1.2m, forming a set of door checks; about 1.7m farther along a projecting slab on the left hand side marks the possible position of a second set. Moving in from the entrance, the badly ruined remains of a guard chamber can be seen within the wall on the right hand side, its former entrance located between the two sets of door checks. A second intra-mural chamber entered from the interior of the broch is located almost opposite the entrance passage. This chamber is rectangular in shape with 'aumries' or small rectangular recesses built into three of its walls. There is no longer any evidence of an entrance to a stairway within the walls, if such existed. The wall of the broch survives to a height of about 4m in the NW interior, but much damage has occurred since the excavation. The excavator left no plans of the excavation, and the finds are recorded only in a letter he wrote to Joseph Anderson in the late 1860s:
"Beginning on the south side, and clearing away the earth and loose stones, we found an oval chamber [this was the guard chamber leading off the entrance passage], with a portion of the converging roof, or dome, remaining, twelve feet six inches long, six feet six inches wide, and about thirteen feet to the highest part of the converging sides. In this preliminary experiment, I obtained the bones of various animals, among which are horns of the deer, bones of a bird, and of the cod and haddock; fragments of various kinds of jaws, the enamel of the teeth retaining its pristine freshness, although the bone bears evidence to the lengthened period of its inhumation. Along with these, the horny portion of two right hoofs of a deer, pared down upon the upper edge; a section of an antler an inch long, chipped and ground at both ends; a rib reduced by grinding to an edge; and several bones sawn across, or fractured by a blow, are indisputable traces of its former occupation by man; while at further end, a shell heap of whelks and limpets adjoined a few small pieces of wood charcoal, above which the marks of fire were plainly visible... The further search for vestiges of man's handicraft did not reveal the finds of implements, etc, which I had expected on first breaking open the cairn; but on the other hand, a varied collection of bones of carnivora and herbivora. There appears to be but one trace of human form divine, - a single vertebra of an adult, while jaws and teeth of many of the lower animals abound. Among these, there appear to me to be teeth of the ox, deer, wolf (?), boar, and stoat, with fragments of fishbones. Among this second lot was a piece of freestone, covered with numerous indentations, all nearly of the same size. One of these passes right through the stone; possibly it was used for grinding some kind of weapon... The effect of intense heat is discernible on the east side of the inclosure, in the reddened and disintegrated stones on that part of the wall. This appears to have been occasioned by a smelting fire, employed for the reduction of iron ore, several nodules of which were mixed up with animal remains, and as if in proof of the supposition, an iron spearhead, five inches long, lay beside the lumps of reduced iron in that place. Further evidence of the occupation by man is adduced by the discovery of burnt grain, bere, and oats, of which I obtained a handful close to the wall, and next to the clay bottom."
From the evidence of the bones and shells we can suggest that food was consumed or kept in the 'guard chamber' as well as in the interior. There is also reasonably good evidence for metal-working as well as for the types of crops grown. However, since the interior was cleared out apparently without regard for stratification, chronology or context, we cannot assume that all of these activities were contemporary with each other or even with the main use of the broch. Enough evidence exists from other sites to show that brochs and their outlying structures were re-used and sometimes altered in much later times, including the period of Norse activity.