As knowledge of the importance and wealth of the Irish monasteries became more widely known, they began to attract the attention of Vikings, who were raiding throughout Britain and Ireland in the 8th century. The most distinctive feature of Irish monasteries, their round towers, were built in response to these Viking raids. Eventually, the Vikings established kingdoms and founded Ireland's first cities along coastal areas, including in neighboring Dublin. The High Kings and lesser kingdoms waged near-continuous war with these Norse-Gael settlers for over two centuries.