Photograph of the Iron Age roundhouse at Wick Valley.

Hut 20, a stone-built round house of the Iron Age or Roman period, is one of the best preserved and most accessible round house settlements on Skomer Island. The round house measures 10m east-west externally by 8m north-south. The door is east facing. The field boundary immediately to the east of the round house kinks east to avoid it, suggesting the hut was already extant when the fields around it were laid out.