The building is unique. It was definitely a temple, since a bronze finger from the cult statue was found in a crevice (the figure might have stood on the pedestal mentioned), and was too far from a fort or road to have been a bath or mausoleum. Ox horns, perhaps sacrificial, were found nearby. Its proximity to a spring has caused the suggestion that it was dedicated to a water goddess, but the masonry is too good to suit a shrine to a local godling. Its skilful construction shows that only the military could have built it.
A broken relief from Rose Hill on Hadrian’s Wall depicts Victory, an eagle, and a round domed building under a tree, which can only represent a structure like Arthur’s Oon. If we accept the carvings alleged on the Oon, it is remarkable that they refer to Victory, and to eagles. It is true that Victory was normally worshipped in the forts, but the easiest interpretation is that the Oon was a tropaeum, an official monument dedicated to Victory, and also commemorating the campaign that led to the establishment of the Antonine Wall. Since the Oon is unlikely to be Agricolan, its dates are limited to the period of occupation of the Antonine Wall. ( text from https://canmore.org.uk/site/46950/arthurs-oon-stenhouse#706544)
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