The moat was connected to the sea, the shoreline being some 100m further north-east than today. In the later part of the 13th century, the castle was strengthened by the addition of four round towers, of which only the north-east survives intact. These three-storey towers had strong splayed bases, with arrow slits below the crenellated parapet. A portcullis was added to the main gate. During the Wars of Scottish Independence, Rothesay was held by the English, but was taken by Robert the Bruce in 1311. It then returned to English hands in 1334, before being taken again by the Scots. Following the accession of the Stewarts to the throne of Scotland in 1371, the castle became a favourite residence of kings Robert II and Robert III, who died here in 1406. Robert II granted the hereditary keepership of the castle to his son John, ancestor of the Earls and Marquesses of Bute. Robert III made his eldest son David Duke of Rothesay in 1401, beginning a tradition of honouring the heir to the throne of Scotland with this title. In 1462 the castle survived a siege by the forces of John of Islay, Earl of Ross and the last Lord of the Isles. During the the early 16th century Rothesay Castle was strengthened again. Construction of a gatehouse keep, extending from the north of the curtain wall, began around the turn of the century, to provide more modern accommodation for James IV. The curtain wall itself was raised up to ten metres in height, the works continuing into the reign of James V. In 1527 the castle withstood another siege by the Master of Ruthven, which destroyed much of the burgh of Rothesay. In 1544, the castle fell to the Earl of Lennox, acting for the English during the so-called "Rough Wooing". The forework is an L-plan structure, which jutted into the moat and was accessed by a drawbridge. The lower floor comprised a vaulted entrance tunnel running into the older castle courtyard. Above, the four storey tower contained royal lodgings, and still bears the royal coat of arms above the door. Also in the early 16th century, a chapel was constructed inside the old castle. Simple in form, the chapel measured around 6m by 9m, and is now the only surviving structure within the curtain wall. The north-west tower was converted into a doocot, and is known as the "Pigeon Tower", due to the nest boxes built into the outside wall. Rothesay was garrisoned for the Royalists during the Wars of the Three Kingdoms, then for the occupying forces of Oliver Cromwell, who invaded Scotland with his New Model Army in the early 1650s. On their departure in 1660, the troops partially dismantled the structure. What was left was burned by the supporters of Archibald Campbell, 9th Earl of Argyll during his rising of 1685, in support of the Monmouth Rebellion against James VII. Following a long period of neglect, the 2nd Marquess of Bute employed 70 men to excavate the ruins, clearing large amounts of rubbish from the castle in 1816-17. But it was not until the 1870s that the ruins were stabilised. The 3rd Marquess, a keen restorer of historic buildings, embarked upon a series of repairs and restorations, following surveys and advice from his regular architect William Burges. His "restorations" continued until 1900, and include the clearing and shaping of the moat, as well as the red sandstone additions to the forework, which reinstated the hall roof while significantly altering the character of the building. From Wikipedia.