The history of Limerick stretches back to its establishment by Vikings as a walled city on King's Island (an island in the River Shannon) in 812, and to the granting of Limerick's city charter in 1197. King John ordered the building (1200) of a great castle. The city was besieged three times in the 17th century, culminating in the famous 1691 Treaty of Limerick and the flight of the defeated Catholic leaders abroad. Much of the city was built during the following Georgian prosperity, which ended abruptly with the Act of Union in 1800. Today the city has a growing multicultural population. Name Luimneach originally referred to the general area along the banks of the Shannon Estuary, which was known as Loch Luimnigh. The original pre-Viking and Viking era settlement on Kings Island was known in the annals as Inis Sibhtonn and Inis an Ghaill Duibh. The name dates from at least 561, but its original meaning is unclear. Early anglicised spellings of the name are Limnigh, Limnagh, Lumnigh and Lumnagh, which are closer to the Irish spelling. There are numerous places of the same name throughout Ireland (anglicised as Luimnagh, Lumnagh, Limnagh etc.). According to P W Joyce in The Origin and History of Irish Names of Places II, the name "signifies a bare or barren spot of land". Similarly, others have suggested that the name derives from loimeanach meaning "a bare marsh" or "a spot made bare by feeding horses". The Dindsenchas (The Metrical Dindsenchas III page 274), attempted to explain the name in a number of ways, connecting it particularly with luimnigthe ("cloaked") and luimnechda ("shielded"). Early history Limerick's early history is virtually undocumented, other than by the oral tradition, because the Vikings were diligent in destroying Irish public records. William Camden wrote that the Irish had been jealous about their antiquity since the deluge and were ambitious to memorialise important events for posterity. The earliest provable settlement dates from 812; however, history suggests the presence of earlier settlements in the area surrounding King's Island, the island at the historical city centre. Antiquity's map-maker, Ptolemy, produced in 150 AD the earliest map of Ireland, showing a place called "Regia" at the same site as King's Island. History also records an important battle involving Cormac mac Airt in 221 and a visit by St. Patrick in 434 to baptise an Eóganachta king, Carthann the Fair. Saint Munchin, the