The castle hugs a rocky coastal ridge of grey sandstone and limestone, and much of the stone from the castle is largely taken from the ridge itself, probably when the site was first cleared.
The local stone was not of sufficient quality to be used for carving details such as windows, however, and accordingly sandstone was brought in from the Creuddyn peninsula, Chester and the Wirral.
This sandstone was more colourful than the local grey stone, and was probably deliberately chosen for its appearance.

The castle has a rectangular plan and is divided into an Inner and Outer Ward, separated by a cross-wall, with four large, 70-foot (21 m) tall towers on each side; originally the castle would have been white-washed using a lime render.
The outside of the towers still have the putlog holes from their original construction, where timbers were inserted to create a spiralling ramp for the builders.
Although now somewhat decayed, the battlements originally sported triple finial designs and featured a sequence of square holes running along the outside of the walls.
It is uncertain what these holes were used for – they may have been drainage holes, supports for defensive hoarding or for displaying ornamental shields.

The main entrance to the castle is through the western barbican, an exterior defence in front of the main gate.
When first built, the barbican was reached over a drawbridge and a masonry ramp that came up sharply from the town below; the modern path cuts east along the outside of the walls.
The barbican features the earliest surviving stone machicolations in Britain, and the gate would originally have been protected by a portcullis.

The gate leads through to the Outer Ward which, when first built, would have been full of various administrative and service buildings.
The north-west tower was reached through the porter's lodge and contained limited accommodation and space for stores.
The south-west tower may have been used either by the castle's constable, or by the castle's garrison, and also contained a bakehouse.
On the south side of the ward is a range of buildings that included the great hall and chapel, sitting on top of the cellars, which are now exposed.
The stubs and one surviving stone arches from the 1340s can still be seen.
Behind the great hall was the tower used by the constable for detaining prisoners; this included a special room for holding prisoners, called the "dettors chambre" ("debtors' chamber") in the 16th century, and an underground dungeon.
On the north side of the ward was a range of service buildings, including a kitchen, brewhouse and bakehouse, backed onto by the kitchen tower, containing accommodation and storerooms.

The Inner Ward was originally separated from the Outer Ward by an internal wall, a drawbridge and a gate, protected by a ditch cut into the rock.
The ditch was filled in during the 16th century and the drawbridge removed.
The spring-fed castle well built alongside the gate survives, and today is 91-foot (28 m) deep.
Inside, the ward contained the chambers for the royal household, their immediate staff and service facilities; today, historian Jeremy Ashbee considers them to be the "best-preserved suite of medieval private royal chambers in England and Wales".
They were designed to form a royal palace in miniature, that could, if necessary, be sealed off from the rest of the castle and supplied from the eastern gate by sea almost indefinitely, although in practice they were rarely used by the royal family.

The royal rooms were positioned on the first floor of a range of buildings that ran around the outside of the ward, facing onto a courtyard.
The four towers that protected the Inner Ward contained service facilities, with the Chapel Tower containing the private royal chapel.
Each tower has an additional watchtower turret, probably intended both for security and to allow the prominent display of the royal flag.
The arrangement was originally similar to that of the 13th century Gloriette at Corfe Castle, and provided a combination of privacy for the king while providing extensive
The castle hugs a rocky coastal ridge of grey sandstone and limestone, and much of the stone from the castle is largely taken from the ridge itself, probably when the site was first cleared. The local stone was not of sufficient quality to be used for carving details such as windows, however, and accordingly sandstone was brought in from the Creuddyn peninsula, Chester and the Wirral. This sandstone was more colourful than the local grey stone, and was probably deliberately chosen for its appearance.
The castle has a rectangular plan and is divided into an Inner and Outer Ward, separated by a cross-wall, with four large, 70-foot (21 m) tall towers on each side; originally the castle would have been white-washed using a lime render. The outside of the towers still have the putlog holes from their original construction, where timbers were inserted to create a spiralling ramp for the builders. Although now somewhat decayed, the battlements originally sported triple finial designs and featured a sequence of square holes running along the outside of the walls. It is uncertain what these holes were used for – they may have been drainage holes, supports for defensive hoarding or for displaying ornamental shields.
The main entrance to the castle is through the western barbican, an exterior defence in front of the main gate. When first built, the barbican was reached over a drawbridge and a masonry ramp that came up sharply from the town below; the modern path cuts east along the outside of the walls. The barbican features the earliest surviving stone machicolations in Britain, and the gate would originally have been protected by a portcullis.
The gate leads through to the Outer Ward which, when first built, would have been full of various administrative and service buildings. The north-west tower was reached through the porter's lodge and contained limited accommodation and space for stores. The south-west tower may have been used either by the castle's constable, or by the castle's garrison, and also contained a bakehouse. On the south side of the ward is a range of buildings that included the great hall and chapel, sitting on top of the cellars, which are now exposed. The stubs and one surviving stone arches from the 1340s can still be seen. Behind the great hall was the tower used by the constable for detaining prisoners; this included a special room for holding prisoners, called the "dettors chambre" ("debtors' chamber") in the 16th century, and an underground dungeon. On the north side of the ward was a range of service buildings, including a kitchen, brewhouse and bakehouse, backed onto by the kitchen tower, containing accommodation and storerooms.
The Inner Ward was originally separated from the Outer Ward by an internal wall, a drawbridge and a gate, protected by a ditch cut into the rock. The ditch was filled in during the 16th century and the drawbridge removed. The spring-fed castle well built alongside the gate survives, and today is 91-foot (28 m) deep. Inside, the ward contained the chambers for the royal household, their immediate staff and service facilities; today, historian Jeremy Ashbee considers them to be the "best-preserved suite of medieval private royal chambers in England and Wales". They were designed to form a royal palace in miniature, that could, if necessary, be sealed off from the rest of the castle and supplied from the eastern gate by sea almost indefinitely, although in practice they were rarely used by the royal family.
The royal rooms were positioned on the first floor of a range of buildings that ran around the outside of the ward, facing onto a courtyard. The four towers that protected the Inner Ward contained service facilities, with the Chapel Tower containing the private royal chapel. Each tower has an additional watchtower turret, probably intended both for security and to allow the prominent display of the royal flag. The arrangement was originally similar to that of the 13th century Gloriette at Corfe Castle, and provided a combination of privacy for the king while providing extensive 
Conwy Castle