The Digital Hadrian's Villa Project (supported by NSF grant # IIS-1018512) has the mission of creating a 3D digital reconstruction and virtual world (VW) of the entire site of this World Heritage site, which is located near Tivoli, Italy. The paper will first discuss the overall aims and methods of the project. It will then focus on the creation of an application in Unity 3D of software that enables us accurately to simulate the apparent path of the sun through the sky on any day and at any hour of the year 130 CE. The motivation behind this application is the discovery of two important solar alignments affecting the design and orientation of two of the thirty major building complexes on the site: the so-called Temple of Apollo in the Accademia; and the lower rotunda of Roccabruna (cf. De Franceschini and Veneziano 2011). Taken together with the recent discovery of a similar solar alignment of the Hadrianic Pantheon in Rome (cf. R. Hannah 2009), these alignments suggest that others may have affected the siting of other buildings at the villa. The application we have embedded within the user interface of our VW makes it relatively easy and efficient to discover new alignments. Bibliography:De Franceschini, Marina and Giuseppe Veneziano. 2011. Villa adriana. Architettura celeste: i segreti dei solsitizi (Rome, Bretschneider).Hannah, Robert. 2009. Time in Antiquity (London, Routledge).
