The Mystery of the Rotating Ceiling in the Domus Aurea

Travis R. Rupp (The University of Iowa)

In the 1930’s the discovery of Nero’s Domus Aurea brought with it a slew of questions and mysteries. Controversy already surrounded the complex because Nero built the massive structure after the great fire in 64 A.D. However, the discovery of the Octagonal Suite (Rotunda), located in the Esquiline Wing of Nero’s palace, seemed to reflect a curious passage in Suetonius. According to the ancient historian, [P]raecipua cenationum rotunda, quae perpetuo diebus ac noctibus vice mundi circumageretur… (Suet. Nero 31.2). This is usually taken to mean that the room revolved, but what neither Suetonius nor any other ancient author explains is how this magnificent spectacle could mechanically work.

In looking at the multiple theories that exist, many problems and controversies stand in the way of preferring one theory as fact. A particular problem is the ambiguity of the Latin text itself. Many scholars wish to interpret Suetonius literally, ignoring the possibility of an exaggeration or metaphor. A balance should be provided by the archaeology of the remains of the Domus Aurea on the Esquiline Hill. In many cases, images of the room are linked with the quote from Suetonius implying that this must be the majestic dining hall from his biographies even though a very small portion of the three hundred acre estate has been excavated.

After examining Suetonius’ language and the archaeological record, the claim that the room rotated is impractical and sufficient evidence is non-existent. However, some theories thinly stretch the evidence that exists (Stierlin 1996). Of course the technology existed for these magnificent mechanical accomplishments. However, after examining similar rotating dome structures in antiquity, such as the temple of the Sassanid King Chosroes II, how Nero made the room rotate is still unanswered.

This brings us to the more recent discussions of this fascinating room (e.g. William MacDonald 1982, K.R. Bradley 1978, and most recently Larry Ball 2003). Bradley and MacDonald are both skeptical of literal interpretations of Suetonius. They point out multiple flaws and gaps in labeling the Octagonal Suite as the rotating dining hall. The most important argument comes from Ball’s detailed study of the remains of the Domus Aurea. In carefully studying the Esquiline Wing of the palace, Ball does not venture guesses on the intended purpose of each room, nor does he address Suetonius’ claim. However, he does examine exactly what the architects Severus and Celer were aiming at in arranging and constructing the palace in the way they did, including which preexisting buildings they chose to raze and which they chose to include as part of the final structure. Ball’s study of the layout and use of light leads me to a closer examination of what could have been the rotating ceiling that Suetonius describes.

After examining archaeological evidence and Suetonius’ text we can conclude that we lack sufficient evidence to support the claim of a rotating ceiling in the Octagonal Suite. However, I will suggest that a plausible solution to this mystery is that the orientation of the structure to optimally use light creates a subtle optical illusion, making the room appear to be rotating in time with the sky. The supposedly moving ceiling is an invention of Suetonius’, because he clearly wishes to highlight the wastefulness of Nero in his description of the Domus Aurea, making him a monster in stark contrast to the Emperor’s Trajan and Hadrian of his day.  The Octagonal Suite, as I reconstruct it, would have been quite extraordinary enough without Suetonius’ exaggeration.