In this video we see screen capture of the simulation of the northern Campus Martius made by the Virtual World Heritage Laboratory, Indiana University and the IDIA Lab, Ball State University. Using data from NASA's Horizons System, the simulation allows the user to change the time of day, day of the year, and year any time in the period 9 BCE to 40 CE. In this video, the simulation is used to test the validity of a thesis first proposed by Edmund Buchner in 1976. Buchner proposed that the Horologium and Ara Pacis of Augustus are aligned in such a way that on Augustus' birthday (September 23), the shadow of the obelisk (which serves as the pointer of the horologium) follows the equinoctial line across a paved plaza. The line can be hypothetically extended beyond the pavements of the horologium to the Ara Pacis immediately to the east. Buchner speculated that the shadow continued through the middle of the Ara Pacis. The simulation shows that this is not the case: the shadow veers to the south as it approaches the western facade of the Ara Pacis and thus does not reach the middle of the altar.