Castle moats: secrets of medieval defense at Thorens Castle
Imagine a mighty fortified castle surrounded by a vast moat filled with shimmering water, which you can cross via a drawbridge. This moat, also called a ditch , has long fascinated lovers of medieval architecture. Follow the guide: let's explore moats, these iconic defensive trenches of fortified castles, and understand why the Château de Thorens , nestled in the mountains, made such a unique choice.
What are moats?
Moats are wide ditches dug around a fortified castle (or part of it) and generally filled with water to strengthen its defenses. In other words, a ditch (defensive trench) becomes a "moat" once water is introduced. True fortifications in their own right, moats encircle the fortress like a protective ring and deter attackers.
From a visual standpoint, moats evoke the classic image of a fortified castle surrounded by a wide canal . They could be very imposing: their width sometimes reached tens of meters, as at the Château du Plessis-Bourré, whose moat is nearly 50 meters wide. These pools of water reinforced the majestic character of the castle. But above all, their role was defensive: a well-designed moat creates a natural barrier between the attacker and the walls (the high fortified walls surrounding the castle).
How were they built?
In the Middle Ages, digging moats was a monumental task carried out entirely by hand. Workers (often requisitioned peasants) dug a deep ditch all around the castle. The excavated earth and rock were frequently reused to reinforce the site – for example, by building up an embankment or thickening the fortress walls. Thus, digging the moats served a dual purpose in defense: it created an obstacle in front of the castle while simultaneously increasing the height or thickness of the fortifications with the excavated material.
For castles that could afford water-filled moats, construction also involved hydraulic engineering. It wasn't enough to simply wait for rain to fill the moat; a constant water supply was essential. Often, a nearby stream was diverted via a canal to fill the moat. If a river wasn't close enough, a reservoir was created upstream, and its flow into the moat was regulated. These systems ensured a stable water level year-round, a crucial condition for the moat to remain effective in case of attack. Naturally, a drawbridge (a movable bridge that can be raised to close access) completed the structure, allowing entry to the castle while also enabling its isolation during a siege.
Why was there water in it, and is there still water in it?
Water is a formidable defensive asset. A flooded moat slows and discourages enemies far more effectively than a simple dry ditch. Attackers cannot easily approach the castle walls, lean their ladders against them, or set up a siege tower to launch an assault. Filling a moat with water was a daunting task for the enemy: it was impossible to fill it quickly or cross it without specialized equipment. Furthermore, water prevented undermining tactics ( digging beneath the foundations to bring down the wall) – without underwater means, it was difficult to mine the walls from the bottom of a flooded moat. In short, moats kept enemies at bay and protected the bases of fortifications. They could even serve as fishponds: in peacetime, fish were raised there, and during prolonged sieges, these fish provided a supplementary food source for the defenders. Finally, beyond the military aspect, the moats added prestige and beauty to the lord's residence: many lords appreciated the reflection of their castle on the calm water of their moats, even in times when the defensive function was secondary.
However, not all castles had water-filled moats , far from it. Sometimes, geography or climate simply didn't allow it. Surrounding a castle built on a steep hill or in the mountains with water was practically impossible. But was this really a problem? Not necessarily, because the natural slope of the terrain then acts as a defense: a castle perched high up benefits from cliffs or steep slopes that enemies will find just as difficult to cross. Similarly, in regions with a dry climate or an unpredictable rainy season, maintaining water-filled moats was a challenge. Dry moats were therefore used instead —that is, simple ditches without water, with sides just as difficult to scale. Some lords, for lack of a better solution, reinforced these dry ditches with traps: sharpened stakes, hidden holes, thorny bushes—anything to make life difficult for unwary attackers. Thus, even without water, the principle remained the same—keep the enemy at bay and protect the fortress.
And what about today? With the evolution of military architecture, many historic moats have been drained or filled in over the centuries, sometimes for sanitary reasons or to redevelop the spaces. Some have become gardens, others verdant ditches that can be crossed by charming little bridges. In any case, whether they still contain water or not, moats continue to tell the story of fortified castles across Europe.
The special case of Thorens Castle
Thorens Castle , perched on the foothills of the Alps in Haute-Savoie, perfectly illustrates how a fortified castle can adapt to its environment. Built on a rocky mountain spur, it never needed—nor could have—a water-filled moat. Its natural topography is its strength: the steep slope around the castle serves as a natural rampart. Instead of being surrounded by a wide, flooded moat, the castle overlooks precipitous slopes that would have been a formidable obstacle for anyone contemplating an assault. It was pointless to try to advance siege towers or fill a moat under the defenders' fire: the mountain itself protected Thorens.
This unique feature only enhances the charm of the place. Thorens Castle, with its dry moat and panoramic views over the valley, offers a living testament to medieval ingenuity in defense . The spirit of the Middle Ages still lingers here, while you can enjoy modern comforts, as this fortified castle has reinvented itself over the centuries. Today, it welcomes visitors and travelers as a castle hotel – a unique opportunity to sleep in the heart of history.
Ready for the experience? Step back in time: book a room now in this exceptional historical setting. Live like a lord or lady of the manor during your stay at Château de Thorens, where every stone still whispers the secrets of the moats and ramparts of yesteryear. You'll never look at castle moats the same way again… especially from your room's window in our castle hotel nestled in the heart of the mountains!