Carrickfergus Castle in County Antrim

Carrickfergus Castle is the best preserved medieval castle in Ireland. It is also the castle that was garrisoned for the longest period; it was only handed over to civilian control in 1928. Approaching Carrickfergus from any direction the first thing to be seen would be the silhouette of the castle. Today it is maintained by the Northern Ireland Environment Agency as a state care historic monument.
  Carrickfergus was built by John de Courcy in 1177 as his headquarters, after he conquered eastern Ulster in 1177 and ruled as a petty king until 1204, when he was ousted by another Norman adventurer, Hugh de Lacy. It appears first in the official English records in 1210 when King John laid siege to it and took control of what was then Ulster’s premier strategic garrison. Following its capture, constables were appointed to command the castle and the surrounding area. In 1217 the new constable, De Serlane, was assigned one hundred pounds to build a new curtain wall so that the approach along the rock could be protected. A chamber on the first floor of the east tower is believed to have been the castle's chapel on account of its fine Romanesque-style double window surround, though the original chapel must have been in the inner ward. The ribbed vault over the entrance passage. The massive portcullis at either end of the gatehouse are later insertions started by Hugh de Lacey who died in 1248 and did not live to see its completion in around 1250 A.D. It was finished by King Henry III.
  After the collapse of the Earldom of Ulster in 1333, the castle remained the Crown's principal residential and administrative centre in the north of Ireland. During the early stages of the Nine Years War (1595–1603). During the sixteenth and seventeenth centuries a number of improvements were made to accommodate artillery, notably externally splayed gunports and embrasures for cannon, though these improvements did not prevent the castle from being attacked and captured on many occasions during this time. General Schomberg besieged and took the castle in 1690. This is also the place where Schomberg's leader, King William III first set foot in Ireland on 14 June 1690.
  In 1797 the Castle, which had on various occasions been used to house prisoners of war, became a prison and it was heavily defended during the Napoleonic Wars; six guns on the east battery remain of the twenty-two that were used in 1811. For a century it remained a magazine and armory. During the First World War it was used as a garrison and ordnance store and during the Second World War as an air raid shelter.

It was garrisoned continuously for about 750 years until 1928, when its ownership was transferred from the British Army to the new Government of Northern Ireland for preservation as an ancient monument. It remains open to the public. The banqueting hall has been fully restored and there are many exhibits to show what life was like in medieval times. It was built and re-built three times, and still stands today.