Font Size

100% 150% 200%

Background Colour

Default Contrast
Close Reset

An Sean Chaisteal, Ardnacross, Mull

Broch (Iron Age)

Site Name An Sean Chaisteal, Ardnacross, Mull

Classification Broch (Iron Age)

Canmore ID 22259

Site Number NM54NE 4

NGR NM 5510 4988

Datum OSGB36 - NGR


Ordnance Survey licence number 100057073. All rights reserved.
Canmore Disclaimer. © Copyright and database right 2020.

Toggle Aerial | View on large map

Digital Images

Administrative Areas

  • Council Argyll And Bute
  • Parish Kilninian And Kilmore
  • Former Region Strathclyde
  • Former District Argyll And Bute
  • Former County Argyll

Archaeology Notes

NM54NE 4 5510 4988

(NM 5510 4988) An Sean Chaisteal (NAT)

Broch (NR)

OS 1:10,000 map, (1976)

Broch, Ardnacross: This broch, known as An Sean Chaisteal, is situated 640m NNE of Ardnacross farmhouse, overlooking the Sound of Mull. It stands on the brink of a rocky cliff 7m high, bordering the shoreline, which lies about 100m to the E. From all other directions the approach is over almost level ground.

The broch wall has been so severely reduced that the tumbled debris now appears as a circular mound of stones, about 2m high, with the centre slightly hollowed. However, a sufficient number of facing-stones are exposed in the surface of the mound to establish that the broch is circular on plan with a wall at least 4m thick enclosing a central court about 10.7m in diameter. The entrance, on the NW, is choked with debris including what appear to be fallen lintel-stones; it is checked for a door. Traces of intramural structures can be seen on the NNE and S, but in the absence of excavation it is not possible to determine their precise size or function.

To the N of the broch a thin scatter of stony debris, which extends for some 17m to the SW along a natural scarp from the crest of the cliff on the E, appears to represent the remains of a defensive outwork, probably a wall, designed to provide extra protection for the broch entrance.

RCAHMS 1980, visited June 1972.

An Seal Chaisteal, a broch. The remains at this site were in a similar condition to that described above when seen in May 1972. Name confirmed.

Surveyed at 1:2500.

Visited by OS (R D) 13 May 1972.


Field Visit (9 June 1934)

Broch, An Sean Chaisteal.

Wall probably 11 ½ ‘ thick internal diameter 33-34’ overall about 57-8’—an outwork to NNW. Very probably a broch.

Cairn (poss).

At point of Rudh an t Sean Chaisteal, a knoll about 62’ in diam looks like a cairn (but might just possibly be a natural outcrop!)

Visited by VGC 9 June 1934

NB This note by VGC incorporated in RCAHMS Emergency Survey 1942-3.

Information from RCAHMS (GFG) 8 January 2012.

Field Visit (30 July 1943)

This site was included within the RCAHMS Emergency Survey (1942-3), an unpublished rescue project. Site descriptions, organised by county, vary from short notes to lengthy and full descriptions and are available to view online with contemporary sketches and photographs. The original typescripts, manuscripts, notebooks and photographs can also be consulted in the RCAHMS Search Room.

Information from RCAHMS (GFG) 10 December 2014.

Publication Account (2007)

NM54 1 AN SEAN CHAISTEAL (‘Ardnacross’)

NM/5510 4988

This broch in Kilninian and Kilmore is in an unusual situation for a western such site, standing as it does on flat, modern farmland next to a short, steep rocky bluff about 9m (30 ft) high and overlooking the Sound of Mull (visited 4/6/64 and 9/10/89). The bluff is probably the edge of a raised beach and it leads down to the rocky shore.


Level 1. The building is almost circular and the exposed entrance passage – facing north-west up the coast – is 4.1m long and 1.1m wide at the outside. There are two lintels still in position (one in situ over the door- frame) and two built door-checks are apparent 1.4m from the outer end. The bar-hole and -socket (on the left) are just visible immediately behind the checks. In 1964 the front lintel had fallen forward but by 1989 it was back in position, its lower face some 20cm below that of the one at the door-frame. It is a large slab, almost a truncated triangle in shape and doubtless originally stood on edge like others in this position. The passage widens to 1.5m behind the checks and narrows again to 1.1m at the inner end. A pit in the wallhead to the left of the entrance may mark the position of a guard cell; there is nothing comparable visible on the right side.

Level 2. Since the inner lintel over the entrance is much thinner than the outermost one it seems likely that there was a hollow in the wall above the whole length of the passage (up to the outermost massive one) – an inwards-facing chamber in fact. Indeed it can be seen that the side walls of the passage – built of large, flattish stone slabs – rise about a foot above the lintel at the door-frame and ought to be the base of the walls of the chamber above. However no sockets for torn-out lintels are apparent.

There are traces of what appears to be a mural gallery on the wallhead from about 8.30 to 9 o’clock and also [2] from about 12.30 to 2 o’clock. In the former place it seems to curve inwards at 9 o’clock before disappearing under rubble. The fragment of gallery is about 1.2m (4 ft) higher than the entrance lintel so it ought to be an upper tier even though it is only about 1.8m (6 ft) above the outside ground surface at this point. The interior is too full of debris for any scarcement to be visible; it is probably buried.

At about 1 o’clock a lintel on the wallhead is visible, at about the height of that over the entrance; it seems to cover a stretch of gallery and the inner face of this is marked on the plan. If the ground on which the broch stands is flat the wall may be about 3m (10 ft) high on the landward side.

There is a possible outer wall on the north side, running towards the beach; the broch entrance is close to it so it may be an outer defence for that.


The unusual situation of this broch on flat ground recalls solid-based brochs on the west coast like Dun Troddan and Dun Telve, and it may be that An Sean Chaisteal is one of those, a more advanced form of tower built more confidently on low-lying ground. The relatively thick wall (below) is appropriate for a solid-based broch.

Dimensions: from 6-12 o’clock the overall diameter is about 18.0m (59 ft), the wall thickness (at the entrance) being 4.12m (13.5 ft). From 9-3 o’clock the overall diameter is 18.61m (61 ft), the internal from 7.93 - 8.24m (16-27 ft). The wall proportion on the latter axis is therefore about 55%.

Sources: 1. NMRS site no. NM 54 NE 4: 2. RCAHMS 1980, 90-1, no. 165 and fig. 89.

E W MacKie 2007


MyCanmore Image Contributions

Contribute an Image

MyCanmore Text Contributions