allegedly showing isis destroying a historic city in northern iraq dating back to the 13th century b.c. using sledgehammers , drills and barrel bombs .
the destruction at nimrud , which took place last month , follows other attacks on cultural heritage sites carried out by the islamic state , which now holds a third of iraq and neighboring syria in its self-declared caliphate .
the video shows the group making barrel bombs which they lined up along the ancient relics inside the ruins of what was once the capital of the assyrian empire .