matea gold of the "washington post," peter nicholas at the "wall street journal," thank you both very much. >> thank you. >> thank you gwen. >> ifill: the united nations cultural agency recently expressed alarm over one of the middle east's most treasured historical sites. they reported that the ancient city of palmyra, syria, home of 2,000 yearr-old ruins, and a u.n. world heritage site, is currently under threat, as islamic state forces move in, fighting against government troops in the area. at this point, the militants have been held at bay, but the destruction and looting of antiquities is one of the turmoil's many casualties. newshour special correspondent marcia biggs reports tonight on the fight to save them. it's part of our series on "culture at risk." >> reporter: it's as stark as night and day. this satellite photo from before and after the war. both are from the ancient city of apamea, founded in 300 bc. it was a hub of commerce and culture in the roman era. and it boasted one of the largest theaters in the ancient world, seating 20,000 people. today it is pockmarked with