Sometime before the later 5th to early 6th centuries AD, the remains of the old broch mound were once again revisited and an elaborate underground passageway, or souterrain, was constructed outside the old entrance to the broch.
The rubble infill of the broch passageway itself was cleared out to form the chamber of this souterrain. The Structure B complex also continued to be active in this phase, with modifications.
The discovery of the souterrain was very good news for us as it allows us to examine another example of a souterrain that is (mostly) undisturbed. A small amount of modern interference was detected while were excavating in 2010. This took the form of a hole that had been made down into the passage, probably in the second half of the twentieth century, and which had been back-filled with soils that included modern china, iron objects and even old timbers.
From 2003 to 2005, excavations were conducted at an extremely well-preserved souterrain, 400m south of The Cairns site, which was brought to light by the geophysical surveys.
The Windwick souterrain appears to have been built in the later Bronze Age and was surmounted by a less well-preserved structure, perhaps a house. The rich artefact assemblage included stone tools, glass beads and jet objects, evidence of butchery and grain processing etc.
Activity here continued into the Middle Iron Age, making it contemporary with the broch-period activity at The Cairns up the hill.
While we were assessing the interior of the souterrain for future full excavation a shaped whale tooth was found, which may originally have been a pommel for an item like a sword.
In Phase 7, the souterrain was closed. Elements of its roof were slighted, and parts of the passageway were filled in. Over its southern end of the souterrain, a new building, Structure H, was built, but only its central hearth, two ephemeral stone settings, and a thin skim of floor deposit survived to indicate the original extent of the building.
To the north and east of where the souterrain had lain, a series of revetment walls and flagged surfaces were built in the form of three roughly parallel tiers of linear kerb, enveloping the remains of the broch mound. The middle line of revetment lay snug against the upper, outer wall face of the broch and incorporated fragments of the old broch entrance passage lintels, distinctive massive, water-worn stones, which must have been finally slighted at this time.
The middle kerb/façade appeared to be screening-off the last remaining visible vestiges of the broch and it lay snug against the broch wall, and ran directly across the slighted portion of souterrain roof.
On the flagged surface immediately above the still intact portion of the souterrain roof, a small, apparently outdoor hearth was set up and has been C-14 dated to between AD 433 and 590.