Trewardreva Fogou is located north of Constantine, just southeast of a minor road opposite the gates to Trewardreva Hall. It is one of the less typical fogous in Cornwall, partly because of its location. Most known fogous are concentrated in West Penwith, while Trewardreva lies further east. This makes it an important example for understanding how these underground or semi-underground structures were distributed beyond their better-known western heartland. The fogou is also unusual because it is not entirely subterranean. Instead, the passage runs beneath a raised mound or hump in the landscape. The original entrance has been lost, but it may once have been a narrow creepway like those seen at other Cornish fogou sites. Today, access is from the southwest end, where a depression leads into the passage through an entrance framed by roofstones and two upright portal stones. These portal stones are modern additions and once supported a metal gate, traces of which can still be seen. Inside, the chamber runs for about 8 metres in a straight line and ends at a low north east opening, now partly blocked with later stonework. Unlike many fogous, which have inward-leaning walls that reduce the span of the roof, Trewardreva has almost vertical walls. This meant that large roof slabs were needed to cover the passage. There are nine main roofstones, with some gaps bridged by secondary slabs, and several lighter coloured stones near the north-east end appear to be modern replacements. The side walls are mostly built from small dry-laid stones, with larger upright stones set at ground level in places. This gives the structure a solid and distinctive appearance. Archaeological finds from the site include a pit filled with ashes at one end and a piece of iron slag, now held in Truro Museum. There are also signs of unroofed extensions at both ends, suggesting that the visible passage may represent only part of a more complex original structure. Trewardreva Fogou is also known locally as Piskey’s Hall, or Pixies Hall on Ordnance Survey maps. Folklore tells of farm workers fleeing the field after hearing strange noises from inside, believing they had heard angry piskeys. This fits a wider Cornish tradition that connects fogous with otherworldly beings, hidden places, and underground danger. Although the site may once have formed part of a larger settlement or enclosure, much of that wider context has been lost. Today, Trewardreva remains a rare, well-preserved, and architecturally distinctive fogou outside the main West Penwith group.