The site is dramatically isolated from the mainland by an earthen bank and a rock-cut fosse, with only a single causeway providing access across this defensive ditch. Once inside, visitors encounter a largely level interior space, save for an intriguing horseshoe-shaped mound surrounded by its own ditch, positioned just south of the entrance. Traces of a low earthen bank can still be seen running along the internal perimeter, hinting at additional fortifications that once protected those within.

The fort’s most fascinating feature lies hidden beneath the surface: an elaborate rock-cut souterrain that demonstrates sophisticated engineering skills. This underground network can only be entered through a southern opening, which drops visitors nearly half a metre into a passage that runs north to south for just over four metres. The passage opens into a central chamber measuring 3.7 metres east to west, complete with architectural details that speak to its careful construction; a small wall cupboard built into the masonry of the north wall, and a curious stone bench supported on two stones along the eastern side. The souterrain extends further through multiple chambers and passages, including a western chamber nearly four metres long and a northern passage accessed through a proper doorway with a lintel and portal stones.

Throughout this subterranean complex, flagstone roofing covers the chambers and passages, which vary in height from less than a metre to 1.4 metres in the central area. Three openings to the surface provided ventilation and alternative access points, though the eastern chamber appears to have been deliberately blocked at some point in its history. The entire structure represents a significant investment of labour and skill, carved directly from the bedrock and enhanced with masonry work where needed, creating a secure refuge or storage facility that would have been virtually invisible from above ground.