Treryn Dinas - Promontory Fort / Cliff Fort
On the far side of Porthcurno cove is the imposing and rugged granite headland of Treryn Dinas or Treen Castle. These cliffs are best known as the location of Logan Rock, a naturally occurring 65 ton rock balanced 100ft (30m) above the sea. However, this is also the site of an Iron Age promontory fort which took full advantage of the natural lay of the land.
The site is relatively complex and extends inland considerably from the headland. Whilst the promontory itself is protected by sheer cliffs to three sides the landward side was heavily defended. These defences consist of three sets of large ramparts and ditches the first, and largest, of which measured nearly 20ft (6.5m) high and 800ft (250m) long. The second rampart is smaller and located a couple of hundred feet (80m) closer to the promontory. The third line of defences are a rampart and ditch running across the "saddle" of the headland where it narrows considerably.
According to local folklore the source of these ramparts and the large number of rocks deposited around the site were the work of the giant Dan Dynas. It was said that bad luck would befall anyone removing stones from the giant's handiwork would. Unfortunately this superstition didn't last as much of the rock was taken away.
Located across the neck of the headland are the outlines of what were possibly two house platforms. Further evidence of habitation comes in the form of sherds of pottery found on the headland along with fragments of charcoal and cremated bone. These all add some weight to the idea that Treryn Dinas may have been a site of religious or ceremonial significance rather than any kind of settlement.