Every castle is interesting in its own way. These ten, however, were very important through history and even today.
The Tower of London
Many famous castles in Great Britain, this one tops them all though. Its history starts with William the Conqueror in 1066. He initially built an wooden fortification, which later(1097) became the famous stone White tower. Slowly 21 towers were built, which form the castle of today. They spread across 18 acres of land. What The Tower of London is most known for is its dungeons, where bloody tortures and executions were conducted. Apart from this its main functions include protection of the royal family and providing a power base in the city of London.
Windsor Castle
Not too far from the Tower of London, in the town of Windsor, is located the famous Windsor Castle. It is the largest occupied castle in the world and shares similar history with the Tower, including the connection to William the Conqueror and a construction, made predominantly of timber. For over 900 years the castle has been occupied, currently by the royal family, it is the home of Queen Elizabeth II. Its history starts with the Saxon kinds of the Dark Ages, which used to spot for their own castles. The dungeons, which used to contain important prisoners, are the most interesting place to visit.
Krak des Chevaliers
This castle is located in Syria and is closely connected to the Crusades(in other words a bunch of knights and poor folk pillaging the Holy lands of the East in the name of God). It played an important role in the first crusade(1031) and kept being a point of interest for both sides of the conflict during later crusades. Famous historical figures like Saladin tried to capture it numerous times. Another point of interest are the Knight Hospitallers, who used the castle as their headquarters.
The Citadel in Cairo
Another castle closely related to the Crusades, the Citadel in Cairo existed since 810. It was a palace at first, but its great strategic location made it necessary to be upgraded into a fortress. Saladin used it between 1176-1183 to defend against the crusaders. It is an impressive structure with thirty feet tall and ten feet thick walls, which is quite different in comparison to the western castles from the same age. Indeed, the citadel is not only interesting because of its history but also because of its architecture, its round towers being a royal pain for siege engines to overcome. Simply put it is the most visited non-pharaoh related attraction.
Tintagel Castle
We've all heard about the legend of King Arthur, but not many of us bothered to know his where he was born. And here it is! Of course King Arthur probably never existed, but this doesn't make the site of his supposed birthplace any less visited. Unfortunately the castle itself is a ruin, you can't sleep in it or find royal persons still occupying it. It is very peculiar because the place is not ideal for a fortification(it stretches across two pieces of land), but it was built anyway. It has been abandoned during 13th and 15th century, which led to its neglect, but it is still a very important historic place to visit.
Caernarvon Castle
We already talked about King Arthur's first home, but what about his buddy Merlin? Well, this is the supposed birthplace of the great wizard(he was born in a cave outside the castle actually). The castle was built in 13th century by King Edward I in Wales. As it happens with such great historical locations, the site was used before. Romans, Celts and Normans built fortifications in the area, the place was that good. Interesting thing to note is how King Edward I was aware of the legends of King Arthur. He wanted to draw comparisons between himself and this legendary figure, and thus the castle was created.
Chateau Gaillard
One of the most beautiful medieval castles, The Chateau Galliard was built by Richard the Lion in 1198. It played a pivotal role during the wars between English and French, and was the scene of the most famous medieval siege in history. The castle used to be magnificent. Overlooking the river Seine it had both land and water as protection as well as three circles of fortifications. Its walls were breached during 3 sieges, made by the French King Phillip II. The first obstacle was eliminated after digging up a tunnel. The second one was more interesting and involved going through an unguarded toilet chute(basic accommodations come at a cost unfortunately). The third and final fortification was overcome in a similar way to the first one - by digging a tunnel. What is so impressive about this whole ordeal was how every sieging technique in the book was employed. Sadly today the castle is in ruins.
Dracula's Castle
The real name of this castle is Bran Castle and it is the birthplace of Vlad Tepes(or Vlad the Impaler), the inspiration for Dracula. Its built on the border between Transylvania and Wallachia (currently in the middle of Romania) and was first mentioned in 14th century. The castle has a long and interesting history, including Teutonic knights, Saxons, Mongols, Hungarians and Ottomans but of course Vlad and his story is the main attraction, that brings people in. Lets just say he was not a very pleasant guy to be around.
Urquhart Castle
It is the castle, that overlooks the Loch Ness lake, Scotland, which automatically makes it super famous. Built in 13th century, it may be famous today because of its lake monster but back then it was a heated point of interest, which frequently changed ownership from the English to the Scottish and vice versa. The castle was directly involved in the events, depicted in the movie Braveheart. Today it is a ruin, but if you want to take a look over the lake in hopes of seeing Nessie, you'll have trouble finding a better spot.
Alnwick Castle
Have you ever wondered how to reach Hogwarts without diving into a wall on the train station or using a flying car? Here is your answer! This famous castle's interior was used in the Harry Potter movies. The structure is in excellent condition, houses the Duke of Northumberland(who uses only a part of it) and is the second largest inhabited castle in England. Very old as well, built in 12th century it played a part in the England/Scotland wars as well as the Wars of the Roses. The castle is also a museum and a popular filming location, which makes it one of the prime places to visit and read about.