Which broch?

Building and rebuilding at Clachtoll

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When we look at the remains of the great drystone tower at Clachtoll, we are struck by how monumental and permanent it seems

The use of such large blocks of sandstone makes an enduring mark on the landscape. The truth, however, is that the broch was far from static and unchanging through time. In fact, there is lots of evidence for major periods of collapse, modification and rebuilding.

A large drystone structure with triangular stone above the doorway

As you approach the entrance, you are confronted by a colossal triangular lintel, the outermost of seven edge-set lintels in the passageway.

 

The outer wall of the broch at the entrance, and perhaps even the triangular lintel itself, was rebuilt at some stage in antiquity: this was demonstrated when conservation work on the wall head showed that the outer face of the broch had been rebuilt on the rubble of an earlier collapse.

 Inside the broch, as you walk to the left interior, you may notice the bulging stonework near the base of the wall, forming a rough ledge.

Image of interior wall showing bulging, irregular stonework at lowest level
interior of broch showing irregular stonework at lowest level, with dashed line to mark

Above this level, the stonework is markedly neater and built on a different alignment. The archaeologists who excavated the broch believe this is a key sign that the original building - probably a broch with a very similar layout - collapsed in the Iron Age and was rebuilt on the ruinous stump of the collapsed original.

Looking closely at the stonework reveals
further clues

The corner of one of the cells, showing that the walls are not bonded

In some of the cells within the broch walls, the outer and inner wall are not bonded, as though the outer and inner walls had been reconstructed rather than built together.

In Cell 2, the tall cell on the landward side of the broch, the character of the stonework is quite different to elsewhere, featuring the use of large upright slabs at its base. In other broch settlements, this style of building is common in secondary rebuilding phases of occupation which usually occurred in the middle Iron Age, between 100 BC and 200 AD.

This tantalising evidence suggests that the original Clachtoll broch may have been built much earlier than the occupation debris found in the interior, which mainly dates to 50 BC to 50 AD, would suggest.

Two radiocarbon dates from material incorporated into the Iron Age floors of the broch were much earlier than the others, perhaps indicating activity at the site as early as 300 BC. Could this be an indication of the original construction date?