 On the hilltop, in the site of the 15th-Century Villa Mellini, rises the Monte Mario Observatory, part of the Rome Observatory, and the Museo Astronomico Copernicano.This location (12°27'8.4"E ) was used as the prime meridian (rather than Greenwich) for the maps of Italy until the 1960s.The side of the hill was the former site of the Villa del Pigneto, built by Pietro da Cortona.