Parts of a Castle – 14 Parts Labeled, Moat to Merlons

All 14 parts on the diagram

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Start here: 7 main parts 7

Keep The great tower of the castle, also called the donjon.
Curtain wall The defensive wall round the courtyard (the bailey), studded with towers.
Towers They stand along the curtain wall. From them defenders could shoot along the face of the wall.
Gatehouse Strong building round the entrance, often the weakest part of the defenses. Built so those inside could control who came in.
Drawbridge A bridge across the moat that can be raised. Often later replaced by a stone bridge.
Moat A deep ditch round the castle, wet or dry. Wet moats were dug in low-lying places.
Arrowslit A narrow opening for shooting arrows or crossbow bolts. The small opening made the defender hard to hit.

The castle 3

Portcullis A wooden grille reinforced with metal, lowered to block the gate passage.
Battlements The protected tops of the walls, towers and gatehouse. Defenders stood there to shoot.
Postern A second door or gate in a hidden place.

The top of the wall 4

Merlons The solid blocks of the battlements, between the gaps.
Crenels The gaps between the merlons, to shoot through.
Wall-walk The walkway along the top of the wall behind the parapet.
Machicolations Openings in the floor of a parapet that juts out on brackets. Through them things could be dropped on attackers at the foot of the wall.

How this list was compiled: Read 2026-09-27. Wikipedia, Castle, https://en.wikipedia.org/wiki/Castle , Common features: the keep (donjon), the great tower; the bailey enclosed by a curtain wall studded with towers for enfilading fire along it; the gatehouse, developed because the entrance was often the weakest part, and the portcullis; moats, wet or dry, wet ones found in low-lying areas and usually crossed by a drawbridge, often later replaced by stone bridges; battlements on curtain walls and the tops of gatehouses, with crenellations (alternating crenels, the gaps, and merlons, the solid blocks), hoardings, machicolations and loopholes; arrowslits through which arrows or crossbow bolts were fired, the narrow slit making the defender a small target; the postern, a second door or gate in a hidden spot; wall-walks. Licence: own work

The drawing: Drawn for this site on 2026-10-05 by script from our own geometry: the castle as a front view across its moat, the wall top as a small 3-D model in one parallel projection. Nothing traced. The forms were checked by eye against photographs and a 1780s print of Bodiam Castle on Wikimedia Commons (round corner towers, twin-towered gatehouse, moat) and against the figures of E. Viollet-le-Duc, Dictionnaire raisonne de l'architecture francaise, 1854-1868, public domain (Machicoulis fig. 9, Creneau figs. 7 and 15, Meurtriere fig. 7). Not to scale and not any one castle. Licence: own work

How it works

The parts of a medieval stone castle from outside its moat, then a length of its wall close up. Start with the 7 main parts, then the castle and the top of the wall.

Read the full guide

Getting in

A moat surrounds the walls, crossed by a drawbridge. The gatehouse guards the entrance, the weakest point, with a portcullis to drop across the passage. A postern is a small hidden side door.

On the walls

The curtain wall runs between towers, with the great keep behind. Along the top, behind the battlements, is the wall-walk; the merlons are the solid blocks and the crenels the gaps. Machicolations let defenders drop things on attackers below.

Merlon is the solid block, crenel the gap: together they are crenellations, the notched top of a castle wall.

Questions and answers

What are the parts of a castle called?

The keep, the curtain wall and its towers, the gatehouse with its portcullis, the drawbridge over the moat, and the battlements along the tops, with merlons, crenels and a wall-walk behind them.

What are the parts of a castle wall called?

Along the top, the battlements: solid merlons with crenels between them, and the wall-walk behind. Below the parapet, machicolations, and in the wall arrowslits.

What is the main tower of a castle called?

The keep, or donjon. In a motte-and-bailey castle it stood on top of the motte, the earth mound.