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Castle Architecture - Natural Defenses

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Natural & External Defenses:

Cliffs, Rivers, Moats, Ditches and Ravelines


Castles were often built on sites that were naturally defensible, for example on cliff tops or mountain tops. If no mountain top or cliff was available then at least a hill could be constructed. Many Mottes in Motte & Bailey castleswere man made. Hard living stone such as granite could render attempts at unermining nugatory.

In flat areas, rivers oftem provided a good defense for at least part of the castle perimeter. If no river existed then sometimes one could be diverted, or a an artificial lake could be constructed. On a smaller scale a moat could be built, again frustrating attempts at undermining. some of the most spectacular castles where built on islands or spits of land extending into seas or rivers.

Where it was impractical to supply water a dry ditch was better than nothing, making it difficult for attackers to get their siege engines up against the walls. In later times, after the introduction of gunpoweder, military engineers srted landscaping the whole surrounding area and building outposts called ravelins.

Castle at Sidon

Cliffs and Mountain Tops

The classic story book castle always has a moat, but moats are only practicable on relatively flat land with a good water supply.

In the Languedoc most castles - and especially the so-called Cathar Castles are built on hill tops, and are protected by sheer cliff faces.

These sheer cligff faces serve the same purpose as moats - namely to keep attackers at a distance and frustrate attempts at undermining. The castle shown on the left is Montségur III, built on the site of Montségur II, the castle built as the Cathars' final defensive position in 1244.

Puilaurens - another Cathar Castle

Photographs of Natural Defences


Walzin Castle, Condroz, Dréhance, Dinant, Namur, Belgium


Predjama Castle is built within a cave mouth,
in the historical region of Inner Carniola, in south-central Slovenia


The Château de Peyrelade, Aveyron, Rivière-sur-Tarn, France.


Orava Castle is situated above the Orava river
in the village of Oravský Podzámok, Slovakia.


Edinburgh Castle, Edinburgh, Scotland

Runkelstein Castle in the territory of Ritten, near the city of Bolzano in South Tyrol, Italy


Riegersburg Castle is situated on a dormant volcano above the town of Riegersburg
in the state of Styria in Austria.


Peñafiel Castle, Valladolid Province, Spain


Buildings built into cliff sides are naturally protected


Burg Kriebstein (Kriebstein Castle), Kriebstein, near the town of Waldheim, Saxony, Germany.


Riegersburg Castle is situated on a dormant volcano above the town of Riegersburg
in the state of Styria in Austria. (another view)

Castles in Rivers, Lakes & Seas


Rivers provide a natural moat, for one, two or three sides of a castle. By siting a castle in the meander of a river a castle builder could get three quarters of a full moat for free, plus a guaranteed water supply.

Similarly, lakes provide a great natural defence against enemy approach in general and undermining in particular.

The picture below is the Lake Palace at Udaipur, now an Hotel.

Rio Tejo, Portugal

Photos of Castles in Rivers, Lakes & Seas


Traku salos pilis (Trakai Island Castle) in Trakai, Lithuania on an island in Lake Galve.


Olofsborg (St. Olaf's Castle or Olavinlinna), Savonlinna, Finland.


Castel dell'Ovo ( Egg Castle) is located on the former island of Megaride, now a peninsula, on the gulf of Naples, Italy.


Château de Sully-sur-Loire, Sully-sur-Loire, Loiret, France.


Castle Stalker, on a tidal islet on Loch Laich, an inlet off Loch Linnhe, Scotland


Mont Saint-Michel, located one kilometre off France's northwestern coast, at the mouth of the Couesnon River near Avranches, Normandy, France


Kizkalesi Castle, Mersin Province, Turkey. A town on the mainland known in Antiquity as Corycus or Korykos, is now known as Kizkales after ancient castle facing the town


Castle de Chillon, Veytaux, Switzerland



Moats and Ditches (douves)


A moat is a deep, broad ditch, generally filled with water, that surrounds a castle, or town. To provide a preliminary line of defense. sharpened stakes were sometimes sunk into the moat to make approach even more difficult.

In some places moats evolved into more extensive water defenses, including natural or artificial lakes, dams and sluices. In later castles the moat or water defences may be largely ornamental. Moats could also double as fish ponds, if kept sufficiently clean.

In Medieval times moats were excavated around castles and fortifications as part of the defensive system of obstacles immediately outside the walls. A moat made access to the walls difficult for siege weapons, such as siege towers and battering rams, which needed to be brought up against a wall to be effective. A water-filled moat made very difficult the practice of undermining, digging tunnels under the fortifications in order to effect a collapse of the defences.

The word was adapted in Middle English from the French motte "mound, hillock" and was first applied to the central mound on which a fortification was erected (see Motte and Bailey), and then came to be applied to the excavated ring, a "dry moat".

Other forms of water defences developed by filling the moat with water and broadening it, to the extent that it resembles a lake, giving birth to the terms Water Palace and Water Castle.

See the aerial view f Kenilworth Castle on the left.

In some cases a water-filled moat was formed by taking advantage of a natural island or peninsula site, or by creating one or more artificial lakes behind a dam. Berkhamsted Castle illustrates a fairly early stage in this development, while Caerphilly Castle shows an advanced one. Kenilworth Castle had extensive water defences controlled by fortified dams and sluices.

A crannog is essentially a natural or artificial lake with the castle built on an island or peninsula, rising more or less sheer from the water. Among the more impressive examples is Castle Cornet, in Guernsey, where the function of the moat is performed by the sea.

Castles with moats or surrounded by artificial lakes are common in France, England, Scotland, Ireland and Wales, found in the Low Countries, and in Germany, Austria, and Denmark. They are also found further into the interior of the Continent. On occasion the moat was mixed with stool, urine and or old rotting food as well as the rotting corpses of dead animals to deter the enemy from even thinking of crossing.

In the post-medieval period, fortresses designed to resist firearm artillery often had a dry moat or ditch, and occasionally incorporated water in their defences as protection against storming: for example the bastion fortress at Olomouc. The polygonal forts developed during the 19th Century, relied heavily on dry moats for close protection.

Over the course of time, many fortified castles were converted into palaces, or other grand residences, no longer primarily fortifications but intended to receive guests, or as living quarters. Surrounding moats or lakes became ornamental. As late as the seventeenth century, French châteaux that were not remotely fortified nor built on traditionally fortified and moated sites, pleasure houses such as Vaux-le-Vicomte, were surrounded by traditional formal moats that isolated the main corps de logis and were bridged by an axial approach.

Moats are not common in the Languedoc, and even where they did exist they were not always filled with water. Good examples of dry moats can be seen outside the cite of Carcassonne, and also inside the city just outside the Chateau Comptal.

dry moat outside the Chateau Comptal at Carcassonne
dry moat outside the Narbonne gate at Carcassonne




Muiderslot |castle in the Netherlands
Caerlaverock Castle, a 13th century castle
on the border of England & Scotland
The moated manor house of Baddesley Clinton in Warwickshire, England
Matsumoto Castle
a Japanese Castle in Nagano Prefecture

Photos of Moated Castles


Burg Vischering (Vischering Castle), Lüdinghausen, North Rhine-Westfalia, Germany.


Rocca Sanvitale (Sanvitale Castle), Fontanellato, near Parma, Italy.


Spøttrup Borg, Spøttrup, Denmark


Château de la Mothe-Chandeniers, Les Trois-Moutiers, Poitou-Charentes, France.





A ravelin is a triangular fortification or detached outwork in front of the bastions of a fortress. Originally it was called a demi-lune.

The ravelin is placed outside a castle opposite a fortification curtain. The edges of the ravelin are sited so that the guns there can sweep fire upon the troops that have to run along the fortification curtain. Ravelins are part of the extensive architecture of star forts developed after the introduction of gunpowder.

The wall facing the castle or fort is low and the angles of the others such that the ravelin provides no shelter to attacking forces if taken or abandoned by defenders.

Ravelines were introduced after the introduction of gunpowder and are typical of the seventeenth and eighteenth centuries.




Learn More about Castle Architecture


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