Inchtuthil / Castra Pinnata

Ptolemy set down the name in Greek as Πτερωτον Στρατοπεδον, Pteroton Stratopedon, meaning winged camp. It has been turned back into Latin as Pinnata Castra, and sometimes as Alata Castra, while the Ravenna Cosmography gives it in the locative case as Pinnatis. Ptolemy's second-century Geography lists it as one of four places belonging to the Vacomagi, and calls it a polis, a town. Whether the place was a native stronghold or a Roman work is not settled. The Romans preferred to put their sites near established native centres and to name them after the earlier settlement, and no purely native settlement is known to have been named by Ptolemy in southern Britain, though such settlements are listed in Ireland, which Rome never occupied. Most Roman sites in the north were temporary marching camps rather than permanent forts, and camps were not usually named — though a camp marked out as the site of a future fort might have been an exception.

Where the place actually stood has been argued over for a century. Burghead in Moray has most often been proposed. In 1922 the archaeologist Ian Richmond argued instead for the Roman legionary fortress at Inchtuthil, north of Perth, which he excavated; his case rested on the place name and on his belief that the fortress had been built with merlons — the raised sections between the gaps of a battlement — which he rendered into Latin as pinnae. O. G. S. Crawford supported the identification in 1949, and it remains the one given by the Royal Commission on the Ancient and Historical Monuments of Scotland.

Later scholars have rejected the Inchtuthil identification. Ptolemy's coordinates place Pinnata Castra on the Moray coast, and both he and the Ravenna Cosmography put it near Tuesis, generally taken to be the River Spey. Plotting the sites in the Geography whose positions are known, and deriving the unknown ones from their relative positions, points to somewhere just east of Burghead. A predecessor of the later Pictish fort at Burghead itself remains a strong candidate; other suggestions have included Inverness, the possible Roman camps at Thomshill near Elgin and Balnageith near Forres, Cluny Hill in Forres, and a site now lost within the Culbin Sands.

Pinnata Castra was one of only four places in Britain from which Ptolemy had astronomical observations. Its longest day was recorded at 18.5 hours against the 17 hours given for London, which makes it the most northerly point at which readings were taken. As the northernmost polis on his list it probably marks the limit of Agricola's advance, since Ptolemy's data for Britain is thought to derive ultimately from that campaign.