Dublin originated as a 9th century Viking settlement. 400 years later, the Normans invaded the town and its surrounding area. The English did not leave till another 700 years. Dublin grew into a large city - in Georgian times it was the second largest city in the Empire, after London. Dublin (and Southern Ireland) finally achived independence from Britain after the Easter uprising (1916) and Anglo-Irish war.
Be sure on your visit to Dublin to visit the Guiness storehouse - sip a pint of the world famous beer in the Gravity Bar.
In the evening, drop in at one of the many charming pubs - try to catch some traditional music and dancing.