Are there any castles in the neighborhood where you live? Unless you live in medieval Europe, chances are there aren't many castles nearby. Of course, Wonderopolis has lots and lots of castles. Many of them have unicorns in the backyard, too…but that's another Wonder for the future.

Wouldn't it have been cool to live back in the days of knights and kings and queens? How neat would it have been to come home to a castle? All your friends would've probably lived in castles, too. It must have been so much fun to invite friends over to swim in your moat.

Well, truth be told, not all kids in medieval Europe lived in castles. In fact, some of you may be wondering whether there really are castles in the world. Or are they just the stuff of fairy tales?

Castles are indeed real. There are many of them around the world that you can visit. You won't find many people building castles today, but they were popular at one time.

Royalty in Europe and the Middle East during the Middle Ages often built castles, which were just fortified homes. Castles are different from palaces, which are huge homes that aren't fortified. Likewise, fortresses are fortified, but aren't used as homes. If you find a fortified structure and it's used by a nobleman and his family as a home, you've got yourself a castle.

Castles were built for about 900 years, starting back in the 9th century. At that time, land was divided into many different territories. Individual noblemen would build castles to live in. Fortification was necessary to defend their home from invaders seeking to take their land.

Castles were built in a wide variety of sizes and styles. They had all sorts of different features. A few features, though, were quite common.

For example, one primary characteristic of most castles is the tower. Many castles feature multiple towers. Towers allowed residents to survey the land around them and spot invaders long before they got close to the castle.

The largest and most strongly-defended tower was called the “keep." The keep was where the royal family would stay in times of crisis. They would often store their most valuable items in the keep, as well.

Moats were another popular feature of many castles. Moats are deep rings of water surrounding a castle. They provided a good defense against attacks, as the only way to cross the moat to gain access to the castle was to cross a drawbridge controlled from inside the castle.

When you think of a castle, you probably imagine a huge structure. Many castles were indeed very large. So where's the largest castle in the world? That all depends on how you define castle

Some people define a castle as a single building, while others define a castle as a group of common buildings fortified as a single complex. In this latter category, the Guinness Book of World Records gives the title of biggest ancient castle to Prague Castle.

Home of the Czech Crown Jewels and the home of the Kings of Bohemia, several Holy Roman Emperors and various presidents of Czechoslovakia and the Czech Republic, Prague Castle is made up of multiple palaces, churches and halls that share a common defensive wall and sit on over 18 acres of land.

Wonder What's Next?

Today’s Wonder of the Day is for all you citizens of Planet Earth!