Today’s Wonder of the Day was inspired by Kier Dorian. Kier Dorian Wonders, “Why do kings build a moat around the castle?” Thanks for WONDERing with us, Kier Dorian!

When you were young, did you ever dream of being a handsome prince or a beautiful princess? Why not? The movies make it look like a good life. Who wouldn't want to spend their days in a majestic castle?

Each morning, you could climb to the top of the parapets and look out over the surrounding countryside. In the afternoon, you could ride your noble steed across the fields that comprise your kingdom. At the end of the day, you could relax by taking a dip in that circular pool that wraps around your castle. What are we talking about? The moat, of course!

If you've ever watched a movie, read a story, or seen pictures of ancient castles, you've probably noticed that they almost always have a deep, wide body of water surrounding them. They weren't designed for entertainment, however. The purpose of a moat was primarily to protect the castle from attack.

As a defense mechanism, moats were very effective. Although they're usually depicted as wide, deep bodies of water, moats were often simply dry ditches. Some moats surrounded the castle itself, while other moats might have enclosed several buildings or even a small town.

Moats filled with water were usually supplied by a nearby source of water, such as a spring, lake, or river. Dams could be built that would control the level of water in the moat. While some fancy moats may have had stone sides, most moats had simple banks of earth left over from when they were dug.

As you've probably learned from movies featuring castles, the medieval times when castles thrived were also violent times. There was no shortage of dangers to worry about. In fact, why do you think castles were built? Simple homes were too prone to plundering and pillaging. Castles, on the other hand, offered safety in the form of strong walls and fortifications.

As a form of defense, moats were quite effective. Castles without moats were vulnerable to attacks from below, since marauders often found the only way to take a castle's inhabitants by surprise was to tunnel underneath the castle and attack from below. Moats, however, made the process of tunneling under a castle nearly impossible.

When moats were filled with water, they were usually deep enough to make it difficult for attackers to wade across. In addition to being difficult to swim with weapons, attackers would be reluctant to try swimming across because they would be too vulnerable to attack from castle guards.

One of the only successful ways to overcome the presence of a moat was to use portable bridges to span the moat. Of course, carrying portable bridges and putting them into place before trying to cross to besiege the castle still allowed plenty of time for castle guards to prepare to defend the castle.

From time to time, you might read stories about moats that contained alligators or crocodiles. While such creatures would provide an extra line of defense, these stories are just myths, as it would be nearly impossible for such animals to survive in a moat. Moats often did contain eels and fish, however. Castle residents would stock moats with these creatures to use for food.

Wonder What's Next?

You don’t have to go 20,000 leagues under the sea to experience life on a submarine. Just head over to Wonderopolis tomorrow and dive in!