This castle held the Coyanza Council in 1050; the old Coyanza was populated and fortified by Fernando II of León in the second half of the 12th century. The current castle was built in the 15th century. It was constructed on the site of older castle that had been erected on the ruins of a fortification dating back to the Iron Age.
The castle consists basically of one articulated front with projections, flanked by turrets overshadowing the tower of homage, with round turrets in the Gales and fronts.
The Broch of Gurness is an Iron Age broch village. Settlement here began sometime between 500 and 200 BC. At the centre of the settlement is a stone tower or broch, which once probably reached a height of around 10 metres. Its interior is divided into sections by upright slabs. The tower features two skins of drystone walls, with stone-floored galleries in between. These are accessed by steps. Stone ledges suggest that there was once an upper storey with a timber floor. The roof would have been thatched, surrounded by a wall walk linked by stairs to the ground floor. The broch features two hearths and a subterranean stone cistern with steps leading down into it. It is thought to have some religious significance, relating to an Iron Age cult of the underground.
The remains of the central tower are up to 3.6 metres high, and the stone walls are up to 4.1 metres thick.