James Ackerman has suggested that the move was a conscious one, designed to screen the secular, even pagan nature of the "Cortile" and the collection of sculptures that Pope Adrian VI had referred to as "idols". Today the lowest terrace is still called the Cortile del Belvedere, but the separated upper terrace is called the Cortile della Pigna after the "Pigna", a large bronze pinecone, mounted in the "niccione", likely to have been the finial of Hadrian's tomb or, as supposed in the Middle Ages, to mark the turning point for chariots in the hippodrome where many Christians were martyred. In 1990, a sculpture of two concentric spheres by Arnaldo Pomodoro was placed in the middle of the upper courtyard.