Complex sentence: There was a fortress here from the earliest times but the first recorded reference is in the Annals of the Four Masters for the year 1154 as the seat of the O'Finaghtys, who owned all the land for miles around.
Split into simpler sentences: There was a fortress here from the earliest times but the first recorded reference is in the Annals of the Four Masters for the year 1154. The site is referred to in the Annals of the Four Masters in 1154 as the seat of the O'Finaghtys, who owned all the land for miles around.