1The paper is part of a special issue of Parthica, published in memory of the late Antonio Invernizzi, distinguished Italian scholar who founded that journal and headed the Turin Centre for Archaeological Research and Excavations in the Middle East and Asia for several decades.

2Preliminary results obtained in the frame of the project “From Firuzabad to the Persian Gulf: Multidisciplinary investigations on the Sasanian period” – jointly directed by the Authors – seem to demonstrate that the very few built-up areas and the streets attested at the Sasanian city of Ardashir Khwarrah were arranged according to a strictly orthogonal layout set within a circular perimeter (with the several concentric and radial traces visible at the site only interpretable as irrigation canals), exactly as already documented at Veh Ardashir, the other famous round city founded by Ardashir I.

3The relevance given by the latter king to circular shapes is similarly emphasised at his fortified residence of Qal’a-ye Dokhtar, where the square throne hall (covered by a dome, i.e. another feature partially recalling a circle) is set within a larger circular perimeter, apparently without functional reasons and likely fulfilling a symbolic purpose.

4The Authors hypothesise that the prominence of circular features in Ardashir I’s urban foundations and some of his architectural achievements is linked to the ideology of kingship and to the concept of khwarrah, frequently symbolised by the rounded diadem and connected to the geometric figure of the circle. In the Authors’ opinion, the emphasis given to circular shapes by Ardashir I was therefore an ideological and propagandistic expedient to present himself as a legitimate sovereign in his struggle against the Arsacid Artabanus IV.