Before 1200 there were large earthen defences erected on high ground to defend the river crossing. Between 1200 – 1212 King John’s Castle was planned and built. In the following centuries it was repaired and extended many times .
In 1642 the Great Siege devastated Limerick and the castle. Siege mines weakened the front wall (East curtain wall) of the castle and countersiege mines carried out during the later and subsequent sieges. To date over 1,000 objects have been excavated including skeletal remains of the siege period.
The remains of a medieval garrison and soldiers quarters was recently discovered close to the sallyport area of the castle and can be viewed from the courtyard.
A number of houses believed to be Viking in origin were unearthed during earlier restoration of the castle are also worth seeing. Between 1690 and 1691 the Williamite sieges led to the signing of the Treaty of Limerick. The Treaty stone said to be the site of the signing of the document can be seen clearly on the far shore of the river from the battlements.
The Pre-Norman Limerick features discovered are both defensive and settlement. Extensive evidence of an early defence system and of a strong earthen rampart, revetted with limestone boulders and protected by a deep ditch, show that King John’s Castle was built on an existing fortification.
King John’s Castle retains many of the pioneering features, which made its construction unique for the day. Its massive gate house, battlements and corner towers await exploration by the visitor while the armoury and its contents remain as evidence of its turbulent history.