For decades, masterpieces by the likes of Pablo Picasso, Vincent Van Gogh, Andy Warhol and Jackson Pollock have been kept in the basement of a museum in Iran's capital Tehran, shrouded in mystery. According to estimates in 2018, the collection is worth as much as $3bn. Only a small portion of the work has been exhibited since the 1979 Iranian Revolution but in recent years, the Tehran Museum of Contemporary Art has been showcasing some of its most captivating pieces. The showcase featured more than 15 works unveiled for the first time, including a sculpture by Jean Dubuffet - marking...