Complex sentence: Clongriffin is situated on an historic site which is significant from medieval times, during which it was the accompanying farmland of the monastic Grange Abbey, situated less than half a kilometre from Clongriffin.
Split into simpler sentences: Clongriffin is situated on an historic site which is significant from medieval times. It was once the accompanying farmland of the monastic Grange Abbey, situated less than half a kilometre from Clongriffin.