It’s a first symbolic step in a homecoming that will long outlast the 10-year Odyssey of ancient myth.

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, ahead of their final return, together with the remaining 146 works, by the year 2048.

But Greek opposition politicians, and some archaeologists, say that’s too long. They say the government should have fought in court to recoup the entire collection quicker, arguing it was looted from ancient sites on Greek islands and smuggled away.

Culture Minister Lina Mendoni said the August deal — which also involved New York’s Metropolitan Museum of Art — was the best possible one it could get.

“A court process is a very arduous affair that requires very strong documentation which, in most cases, we lack,” she said Tuesday at a presentation of the exhibition, which opened last week and will run for a year at the Athens Museum of Cycladic Art — itself based on a private Greek collection.

“It is an unfortunate fact that finds from illegal excavations exist all over the world,” she added. “So, whichever of these belong to Greece, our policy is to bring them back.”