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Castlelaw Hill Fort

Iron Age hill fort

Castlelaw Hill Fort

An Iron Age hill fort with a souterrain built in one of the ditches.

An Iron-Age stronghold

On the lower slopes of the Pentland Hills lies an impressive defensive earthwork, more than 2,000 years old. Three concentric rings of ramparts and ditches girdle a low foothill. There are no signs of internal structures, but the middle ditch has a stone earth house built into a section of it.

Revealing evidence

Archaeological excavations in the 1930s and 1940s revealed the site’s long and complicated history. It began in the middle centuries of the 1st millennium BC with a farming community who enclosed their houses within a sturdy timber palisade. This palisade was later replaced by an earthen rampart and ditch. A strong timber gateway controlled access into the fort. Later still, two additional ramparts and ditches were added. This development seems to have been typical of Iron-Age forts in SE Scotland.

An underground mystery

The chief delight of a visit to Castlelaw is exploring the underground feature in the middle ditch. Archaeologists call them earth houses or souterrains. They are also found in Brittany and elsewhere. In Scotland they are found all along the eastern seaboard from Midlothian to the Northern Isles; quite a few are in Historic Scotland’s care. Those on the mainland are similar to Castlelaw’s, with long, curving stone passages.

Castlelaw’s earth house is 20m long with a large, round side chamber. It is sunk into the ditch and so dates towards the end of the hill fort’s existence – the 1st or 2nd century AD. But what it was used for is a mystery. It may have been a hiding-place, a ritual structure or an industrial workshop. Perhaps the most plausible theory is that the cool, dry chamber was used to store cereals and dairy products.

  • The location – on the lower slopes of the Pentlands, an attractive regional park with good walks and wildlife.
  • The ditches – try to trace all three around the hill.
  • The earth house – crouch along the passage, then crawl into the side chamber and wonder what the Iron-Age used it for.


Bus Parking Car Parking Strong Footwear Recommended Strong Footwear Recommended


Region – Edinburgh and the Lothians

On Castle Knowe, about 1m north west of Glencorse or 2.5m south west from Lothianburn Junction on the City Bypass, off the A702.

Grid reference - NT 229 638.