Dover Castle. Dover Castle is a medieval castle in Dover, Kent, England. It was founded in the 11th century and has been described as the Key to England due to its defensive significance throughout history. Some sources say it is the largest castle in England, a title also claimed by Windsor Castle. This site may have been fortified with earthworks in the Iron Age or earlier, before the Romans invaded in AD 43. This is suggested on the basis of the unusual pattern of the earthworks which does not seem to be a perfect fit for the medieval castle. Excavations have provided evidence of Iron Age occupation within the locality of the castle, but it is not certain whether this is associated with the hillfort. The site also contains one of Dover's two Roman lighthouses, one of only three surviving Roman-era lighthouses in the world, and the tallest and most complete standing Roman structure in England. It is also claimed to be Britain's oldest standing building. Built in the early 2nd century, the 5-level 8-sided tower was made of layers of tufa, Kentish ragstone, and red bricks. The castle lighthouse survived after being converted into a belfry in the Saxon era, having a new upper layer added, and was partially renovated in 1913-1915. The remains of the other are located on the opposing Western Heights, across the town of Dover. After the Battle of Hastings in October 1066, William the Conqueror and his forces marched to Westminster Abbey for his coronation. They took a roundabout route via Romney, Dover and Canterbury. From the Cinque Ports foundation in 1050, Dover has always been a chief member, it may also have been this that first attracted William's attention, and got Kent the motto of Invicta. In the words of William of Poitiers: Then he marched to Dover, which had been reported impregnable and held by a large force. The English, stricken with fear at his approach had confidence neither in their ramparts nor in the numbers of their troops. While the inhabitants were preparing to surrender unconditionally, greedy for money, set the castle on fire and the great part of it was soon enveloped in flames. having taken possession of the castle, the Duke spent eight days adding new fortifications to it. The Castle was first built, entirely out of clay. It collapsed to the ground and the clay was then used as the flooring for many of the ground-floor rooms. In 1088, eight knights were appointed under tenures to guard Dover Castle, their names were: William d'Albrincis; Fulberl de Dover, William d'Arsic; Geoffrey Peverell; William Maminot; Robert du Port; Hugh Crevecoeur; and Adam Fitzwilliam. It was during the reign of Henry II that the castle began to take recognisable shape. The inner and outer baileys and the great keep belong to this time. Maurice the Engineer was responsible for building the keep. From 1179 to 1188, the King spent over E6,500 on the castle, an enormous sum, considering that his annual revenue was likely around E10,000. In 1216, during the First Barons' War, a group of rebel barons invited the future Louis VIII of France to come and take the English crown. He had some success breaching the walls, but was ultimately unable to take the castle. The vulnerable north gate that had been breached in the siege was converted into an underground forward-defence complex, and new gates built into the outer curtain wall on the western and eastern sides. During the siege, the English defenders tunnelled outwards and attacked the French. During the time of Stephen de Pencester, a windmill was erected on Tower 22, which was later known as the Mill Tower. By the Tudor age, the defences themselves had been superseded by gunpowder. They were improved by Henry VIII, who made a personal visit, and added to it with the Moat Bulwark. During the English Civil War it was held for the king but then taken by supporters of the Parliamentarians in 1642 without a shot being fired. Knowing the castle was lightly guarded, a local merchant Richard Dawkes accompanied by 10 men scaled the cliffs and attacked the porter's lodge, obtaining the keys and entering the castle before the garrison was summoned. Dover Castle was a crucial observation point for the cross-channel sightings of the Anglo-French Survey, which used trigonometric calculations to link the Royal Greenwich Observatory with the Paris Observatory. This work was overseen by General William Roy. Massive rebuilding took place at the end of the 18th century during the Napoleonic Wars.