The ruined castle remains at Halton which stands on a prominent hill of red sandstone and overlooks the estuary of the River Mersey to the north and east. The first castle on the site was a motte and bailey timber castle built by Hugh Lupus, Earl of Chester, in circa 1070. This was formed by cutting off the highest part of the promontory on the north western side by a ditch 8 metres wide and utilising the natural platform on the rest of the hilltop as a bailey. The castle was occupied by Nigel, the first baron of Halton. In the subsequent three centuries the phases of building and rebuilding in stone are obscured since all rebuilding took place after scraping the previous phase off the bedrock and rebuilding on that foundation. By circa 1250 the curtain wall had been built, together with a square tower on the west side, a round tower at the north end, and stone buildings in a range along the north western side. During this period, from the 11th to the 13th centuries, the ownership passed to the Lacy family, the Lords of Pontefract, who became Dukes of Lancaster in 1311. In the 15th century a gatehouse was constructed. The castle was used as a prison for Roman Catholic recusants in 1579. It was besieged and captured by Sir William Brereton in 1643 and partly demolished on Cromwell's orders in 1644. In 1738 the gatehouse was replaced by a new courthouse and prison and a series of small lock-ups built in the castle interior.
Nothing remains of the early timber castle phase of the buildings and the ditch of the early motte site was filled in the 13th century. The curtain wall only survives as foundations. The stone tower dates from the 13th century and measures 12 metres square at the base. Next to this are the foundations of the kitchen range. In circa 1800 the walls of a folly were constructed to the east of the courthouse where they still form a castellated feature.