The monument comprises the remains of Dunollie Castle, visible as an upstanding monument, together with earthworks relating to the Dark Age and medieval occupations of the site.
The monument was first scheduled in 1931 and rescheduled in 1993, but only the upstanding remains of the castle were included. The present rescheduling rectifies this by taking in the earthworks to the N of the castle.
Dunollie Castle is situated upon the summit of a rock promontory towards the N end of Oban Bay. The existing remains comprise a tower house with an associated bailey (or courtyard), standing on the SW portion of the promontory, together with fragmentary traces of an outer enclosure which surround the remaining area of the summit. The tower occupies the NE portion of the courtyard, the remainder of which is enclosed by a curtain wall and contains traces of internal buildings. The greater part of the castle may be ascribed to the 15th century, but some portions of the curtain wall appear to be of later date.
The tower house is almost square on plan and measures 12m from E to W by 11.3m transversely. It incorporates four main storeys, each of which comprises a single apartment, the lower floor being a barrel-vaulted cellar. The tower has an overall height of about 14m.
The courtyard measures about 24.4m square and was formerly enclosed by a curtain wall. This is now reduced to its lower courses, except on the N and E sides.
About 9m E of the SE angle of the courtyard, a natural defile, which provides a possible way of ascent to the summit, has been sealed off by a well-constructed wall of rubble and lime mortar. Traces of ramparts can also be seen on the N side of the castle. These defences may have been associated with an earlier Dark Age fortress.
Dunollie was the chief stronghold of the Lorn kings in Northern Dalriada. It is said to have been captured and burnt in AD 698 and afterwards re-built by Selbach, ruler of Northern Dalriada. During the early Middle Ages, the lands of Dunollie formed part of the extensive MacDougall lordship of Lorn, and it remained a stronghold of the MacDougalls until the early 18th century when it was abandoned in favour of a new house on an adjacent site.
The area to be scheduled includes the remains described and an area around them within which related material may be expected to survive. It is irregular in plan, with maximum dimensions of 150m N-S and 83m E-W, as shown in red on the attached map.