Complex sentence: Luni had been reduced to a small village at the time of the Lombard king Liutprand, later, it was a countship see under Charlemagne, exactly on the border between the Kingdom of Italy and the Papal States.
Split into simpler sentences: Luni had been reduced to a small village by the time of the Lombard king Liutprand. Later, it was a countship and see under Charlemagne, exactly on the border between the Kingdom of Italy and the Papal States.