Granton Castle, although it no longer exists, was one of the oldest buildings in the area.
The castle was already in existence in 1479, when it was owned by John Melville of Carnbee, Fife, and called Grantoun House. The castle was sacked in 1544 when the Earl of Hertford landed nearby with an English army. In 1619 Granton Castle became the property of Sir Thomas Hope of Craighall, who made great alterations and converted it into a family mansion. Sir Thomas occupied the castle as his principal residence during the reign of Charles I, when it was owned by John Melville of Carnbee, Fife, and called Grantoun House. The Melville family sold it to John Russell in 1592, and it was sold again a number of times after that. The building was repaired and was extended in the mid-seventeenth century by the owner at the time, Sir Thomas Hope.
The Duke of Argyll and Greenwich bought the Barony of Wester Granton, including the castle and the nearby Caroline Park, in 1740 and renamed it Royston Castle. But by 1794 the castle was a ruin and seems to have stayed that way for over a century. In 1928 it was bought by a firm called Bain & Brown who demolished it to quarry the stone underneath it. The castle had stood on a slightly raised area, but the quarrying reduced this. Only one section of wall was left.
The following links are to excellent photographs on Flickr, submitted by ‘arjayempee’.