The castle occupies a naturally fortified position, separated from the mainland to the west by a deep rock-cut fosse, whilst the remaining sides drop steeply to the sea below. First mentioned in records from 1174 when Henry II granted it to Earl Richard, the castle formed an integral part of the medieval borough of Wicklow. Some archaeologists suggest it may have been built atop an even earlier promontory fort, though evidence for this remains inconclusive.

The castle's most distinctive feature is its unusual triangular keep, constructed from uncoursed rubble that has weathered centuries of coastal storms. Along the western side, facing the defensive ditch, a wall survives to about 1.2 metres in height, punctuated by a central gap reached via what appear to be modern rock-cut steps. At the corner where the western and southeastern walls meet, visitors can spot the remnants of a roughly quadrangular tower rising to approximately 4 metres, complete with two arrow loops; a smaller one facing south and a larger opening to the southwest. These defensive features extend beyond the main wall lines, providing additional coverage of the approaches.

The southeastern wall, built upon a sturdy plinth, preserves some fascinating medieval details despite its ruined state. At its seaward end, it reaches 3.5 metres high and contains a garderobe chute, with a small gully carved into the rock below to channel waste towards the sea; a practical reminder of daily life in the castle. The curved northern wall retains a doorway measuring 1.2 metres wide, positioned just above where it joins the southeastern wall. Though the interior is now uneven and overgrown, traces of what's likely a more recent rectangular structure can be seen cut into the rock in the southwestern corner. The castle has been protected as a National Monument since 1940, ensuring this evocative ruin continues to tell its story to future generations.