For decades, an important part of Greece’s cultural heritage sparkled only for the very few in a U.S. billionaire’s private collection, until a groundbreaking deal for its gradual return to Athens. Now 15 of the prehistoric masterpieces have gone on public view for the first time in a temporary display in Athens. This display is coming ahead of their final return, together with the remaining 146 works, by the year 2048. Greek opposition politicians, and some archaeologists, have said that's too long. But Culture Minister Lina Mendoni said Tuesday that the August deal — which also involved New York’s Metropolitan Museum of Art — was the best possible one Greece could get.