This structure was completely below ground with raised entrances level with the surface and was aligned north-east to south-west. The north-east entrance was 53cm above the chamber roof and measured 7m long by 1m wide. The entrance was capped by corrugated iron covered in concrete, but it was not possible to ascertain the width of the lip on which this sat as this cap was the only intact cover on the entire site. The south-west entrance was 55cm above the chamber roof and measured 5.75m long by 1m wide. This was also capped with concrete-covered corrugated iron, which sat on a lip that was 5cm deep at the sides and 10cm deep at the chamber end of the entrance. The north-east entrance had eleven steps leading down into a corridor; the south-west entrance had twelve. Both corridors terminated in an 87cm-deep recess with a 10cm diameter exhaust vent centrally-located in the roof. The floors were each of poured concrete with five 60cm by 46cm concrete slabs set into them.
The central chamber measured externally 7.4m by 1.85m by 2.45m high with an internal measurement of 1.28m at its widest point. This indicates much thicker walls than the other shelters on the site. The chamber was of unpainted concrete and had a bench extending along the external wall on either side. These benches were 45cm high by 33cm deep and were formed of the same concrete as the entire structure. Evidence of shuttering is clear and the principle of the construction technique is similar to that of the other shelters, although, in this instance, fewer facets were poured than in either those types on Area C2 or the other type on Area J1, ie seven were visible above the benches here. Sixteen 60cm by 46cm rectangular slabs extended down the centre of the chamber. Three more exhaust vents were located at equal intervals within the roof.
Both the recess and the internal doorways had the remains of iron hinges and the internal door had the remains of an iron latch, indicating that doors were at one time present. Iron hook latches were affixed to the external wall of the entrance approximately 1m off the floor. <1>