Using NASA data and new computer simulations, researchers say they've discovered how the sun would have lined up with an Egyptian obelisk and the famed Ara Pacis in ancient Rome. The Ara Pacis, or "Altar of Peace," was dedicated in the year 9 B.C. to honor the Pax Romana, an era of relative peace established by Rome's first emperor Augustus. But in ancient times, it would have stood in the northern outskirts of the city, near an Egyptian obelisk that the Romans uprooted from Heliopolis and repurposed as a gnomon, or giant sundial. Many historians had long accepted German scholar Edmund Buchner's theory that the shadow of the obelisk (which now sits in theÂ Piazza Montecitorio) would hit the center of the facade of the Ara Pacis on Augustus'Â birthday, Sept. 23.