Meridian vs. Horologium-Solarium

For years, scholars accepted the hypothesis that the obelisk served as the gnomon of a vast sundial, the so-called "Horologium-Solarium", which recorded the hours of the day and days of the year, as seen in the diagram below with sundial superimposed in red on the groundplan of modern building. Most scholars now recognize that there is no evidence for such a vast sundial and that the obelisk served instead as the gnomen of only a single median, charting the length of the shadow cast at midday each day. Buchner's discovery of the meridian and inscription remains a major achievement.