Yet St. Senan founded two convents for nuns, and was actually on a visit to one of them when he died. Legend has it that when St. Cannera died, she willed it that she should be buried near Senan. To stay true to his own edicts, Senan waited until low tide to bury her in the inter-tidal zone, which was not officially part of the "island", thus fulfilling his sister's wish while not breaking his own rules. Senan was buried in the abbey church of Iniscathay on 8 March, on which day his feast is observed. One of the earliest references to the Round Tower of Inniscathay is in the Irish life of St. Senan. The Vikings first raided Inis Cathaigh in 815, killing many of the monks. The monastery was plundered repeatedly until the Vikings came to settle there themselves in the mid-tenth century. This, in turn, led to attacks by Irish kings. Inis Cathaigh was a part of the Norse Kingdom of Limerick, which included not only Limerick itself but also several other bases in western and even northern Ireland. Given its strategic location at the mouth of the Shannon estuary, it effectively controlled all maritime traffic up the Shannon to Limerick. The Annals of Inishfallen record that during the 970s, Norse kings of Limerick were resident at Scattery Island. In 974, Maccus mac Arailt, King of the Isles captured Ivar of Limerick, but he "escaped over sea" the following year. Ivar of Limerick (last Norse king of the city), along with two of his sons, was slain on Inis Cathaigh by Brian Boru in 977. Scattery Island Cathedral and monastery is an early Christian place of pilgrimage, where St Senan, Bishop and confessor, founded a monastery, in the Shannon estuary, 5 km southwest of Kilrush, County Clare, Ireland. There are the remains of his oratory and house and of seven rude churches or chapels, together with a "round tower" and a holy well still in repute. It is fortified and marked by a lighthouse. At an early period the abbot-bishop of the monastery was considered to exercise authority over what later became the dioceses of Killaloe, Limerick and Ardfert. After the Synod of Ráth Breasail in 1111 a canonical diocese of Inis Cathaig (the spelling then current) was established.