Sweeping in on huge wooden ships holding over a thousand men each, the Vikings came all the way from places like Norway to establish settlements in Ireland. The Vikings were able to do this by sailing through the Irish Sea to coastal areas like Dublin and Cork. They then set up longphorts, or fortresses designed to defend themselves and their ships.
Dublin is located on a bay at the mouth of the River Liffey. Human settlement in Dublin is believed to have begun in 998 A.D., but there were people who lived there before then, just not in settlements. Being located near water has made Dublin a major hub in Ireland for trade and business as ships carrying goods and people from other countries would dock here. Many ships came in and out of Dublin, and allowed the Vikings to travel further inland to other settlements in Ireland. Once word spread that Dublin was a port where people could sell their goods, merchants and traders from all over Europe came.
Dublin is special among other places in Ireland because of how close it is to the Irish Sea and also to England, one of the other countries that the Vikings were invading. Its position made it easy for trade between the Scandanavian countries (Norway, Denmark, Sweden, and Finland), England, Scotland, and Ireland.
