Spectacular 2,000-year-old Hellenistic-style wall paintings have been revealed at the world heritage site of Petra through the expertise of British conservation specialists. The paintings, in a cave complex, had been obscured by centuries of black soot, smoke and greasy substances, as well as graffiti. Experts from the Courtauld Institute in London have now removed the black grime, uncovering paintings whose "exceptional" artistic quality and sheer beauty are said to be superior even to some of the better Roman paintings at Herculaneum that were inspired by Hellenistic art. Virtually no Hellenistic paintings survive today, and fragments only hint at antiquity's lost...