The most significant result of the 2005 season at the Circular Forum in Durrës was gained by the examination of the square podium that forms the foundation for the Rotunda. A trial excavation on the final day revealed the depth of this square base to be at least 2.20 m, on which the Rotunda was
set c. 1.25 m below the level of the Forum paving, making a combined substructure of at least 3.50 m. The square foundation consists of solid rubble concrete with a hard grey mortar of significantly higher quality than that visible in other structures in and around the Forum. There are many fragments of brick and ceramics visible in the now eroded core of the Rotunda. In the podium there was one piece of architectural spolia where a block of limestone, possible a cornice fragment, was incorporated to serve as a cornerstone of the foundation. The podium was created by filling an excavated trench c. 4.0 m deep below the level of the Forum that had cut away all existing structures with layers of rubble concrete up to the level where the Rotunda began. It was observed in both trenches that the upper corners of the square foundation were left rough and unfinished and were always intended to be covered. The massive scale of the foundation invites conjecture regarding the superstructure it was intended to support. It is likely to have been a tall construction, perhaps even a columnar monument. This will have been the focus of a major public space in Dyrrachium. The evidence so far obtained indicates a construction date not before the early 4th century.