>> reporter: michael dante consults for the state department on what he sees as isis's systemic looting of the middle east's ancient past. >> they actively promote looting among their fighters as a way to generate income for the organization. they don't make this is a secret. it's done brazenly, very overtly. >> reporter: if february, isis destroyed statues a at the mow sewell. in october, it was the 1,800-year-old arch blown up. images that caused worldwide condemnation. but there's something isis isn't showing you, and that's what it's keeping and selling. this hercules is a museum piece. this piece of pottery from a repository in raqqah, still bearing its number. it is the smallest items that pose the biggest problems. dante shows is us ancient gold coins and glass, even figurines, most likely robbed from graves