Arthur's O'on temple

One manuscript of the Historia Brittonum by Nennius refers to Arthur's O'on as a "round house of polished stone" by the River Carron, attributing it to Carausius, in a passage primarily referring to Septimius Severus. John of Fordun in the 14th century recorded in his Chronica Gentis Scotorum that the structure was built by Julius Caesar to mark the northern limit of the Roman Empire, and another more fanciful belief that was once popular was that Caesar used it as a secure quarters in which he slept, the building being dismantled stone by stone to be re-assembled at the emperor's next stop for the night. George Buchanan in the 16th century saw it as a memorial to some great Roman victory…

The O'on was built of dressed freestones which were not mortised into each other and no mortar was used. Each stone had a lewis hole in it to allow secure lifting with a hinged pair of metal callipers. The perpendicular height, from the bottom to the top of the aperture, was 22 ft; the external circumference at the base, 88 ft; internal circumference, 61 ft; external diameter at the base, 28 ft; internal diameter, 19 ft; circumference of the aperture, 86 ft; diameter of the aperture, 11 ft; height of the door from its basis to the top of the arch 9 ft; breadth of the East facing door at the base, 6 ft; height, from the ground to the top of the key-stone of the door, 10 ft; breadth of the…