King John Castle (Irish: Caislean Luimnigh ) is a 13-century castle is located on Kings Island in Limerick, Ireland, next to the River Shannon. Although the site dates back to 922 when the Vikings lived on the island, the castle itself was built on the orders of King Johan in 1200, one of the best preserved Norman castle in Europe, walls, towers and fortifications remain today and are of interest.  the remains of a Viking settlement discovered during archaeological excavations at the site in 1900. 
before the castle
The Viking Sea King, Thormodr Helgason, built the first permanent Viking stronghold on Inis Sibhtonn (Kings Island) in 922. He used the base to plunder the length påfloden Shannon from Lough Derg to Lough Ree, pillaging ecclesiastical settlements. In 937 Limerick Vikings clashed with Dublin on Lough Ree and were defeated. In 943 they were defeated again when the head of the local Dalcassian clan joined with Ceallachán, king of Munster and Limerick Vikings were forced to pay tribute to the clans. The power of the Vikings never recovered, and they fell to the level of a minor clan, but often play key parts in the endless power struggles of the next few centuries.
The arrival of the Anglo-Normans to the area in 1172 changed everything.Domhnall Mór Ó Briain burned the city to the ground in 1174 in an attempt to keep it from the hands of the new invaders. After he died in 1194, the Anglo-Normans finally captured the area in 1195 according to John, Lord of Ireland. In 1197 Limerick was given its first charter and its first mayor, Adam Sarvant. A castle, built on the orders of King John, and which bears his name, was completed around 1210.
The castle was built on the border of the River Shannon to protect the city from the Gaelic kingdoms of the west, and from all the rebellion of the Norman lords in the east and south. [ Citation needed ] During the general peace imposed by the Norman rule Limerick flourished as both a port and a trade center, partly because of the castle that serves as a watchdog on all cargo passing through the port of Limerick.  at this time, the city was divided into an area known as the “English town” at Kings Island, while another settlement, named “Irish town” had grown on the south bank of the river.Limerick city became so rich during this time King John set up a mint in the northwest corner of the castle, with pennies and half pennies from this time is to see in Limerick Museum today.  A 1574 document prepared for the Spanish ambassador testify to its wealth:
Limerick is stronger and more beautiful than all the other cities in Ireland, well walls with sturdy walls carved marble … There are no entrance except the stone bridges, one of the two that has 14 arches, and the other 8 … for the most part the houses are square stone of black marble and built in the shape of towers and fortresses. [ citation needed ]
Luke Gernon, an English-born judge and lives in Limerick, wrote an equally flattering view of the city in 1620:
“A lofty building of marble, in the high street, it is built from one port to another in a form colleges in Oxford, so magnificent that at my first entrance, it did surprise me.” 
Siege of Limerick
The walls of the castle was severely damaged in the 1642 Siege of Limerick, the first of five sieges of the city in the 17th century. 1642, the castle was occupied by Protestants fleeing Irish rebellion 1641och besieged by an Irish League of strength during Garret Barry. Barry had no siege artillery so he undermined the walls of King John castle by digging away their foundations.Those inside surrendered shortly before Barry collapsed walls. But such was the damage to the wall foundation as a part of them had pulled down afterwards.
Between 2011 and 2013, the castle underwent a massive transformation, with € 5.7 million spent to improve the facilities visitors of the castle. Among the improvements was a new visitor center, interactive exhibits with computer-generated animation and a cafe overlooking the courtyard and river. 
- King John of England
- History of Limerick city
- Limerick City Museum, just south
- Jump up ^ “Irish visitor attractions – King John Castle”. Heritage Ireland. Retrieved twelve October, 2013.
- Jump up ^ http://limerickslife.com/limerick-castle/
- Jump up ^ “800 years of history.” Discovery Ireland. Retrieved 13 October, 2013.
- ^ Jump up to: ab “Castle History”. teachnet.ie. Retrieved 13 October, 2013.
- Jump up ^ Gernon, Luke A Discourse of Ireland in 1620, edited by CL Falkiner 1904
- Jump up ^ “King John Castle”. Shannon Heritage. Retrieved twelve October, 2013.