PALMYRA WATCH: Jihadists destroy Syria’s infamous Palmyra prison (AP/Times of Israel). As far as I'm concerned, ISIS is welcome to blow up all the empty Baathist prisons they can find. That said, I very much doubt that their own detention facilities are havens of human rights.
Otherwise, I can find little news about Palmyra's antiquities and ruins. This article from the London Times says that antiquities were cleared out of the Palmyra Museum by Assad-loyalist militias before Palmyra's fall. The full article is behind a subscription wall, but the visible first two paragraphs have some information.
Background here and links.
