A beam of light shining through the oculus.The height to the oculus and the diameter of the interior circle are the same, 43.3 metres (142 ft), so the whole interior could house a sphere 43.3 metres (142 ft) in diameter). These dimensions make more sense using ancient Roman units of measurement: The dome spans 150 Roman feet and the oculus is 30 Roman feet in diameter. The Pantheon still holds the record for the world's largest unreinforced concrete dome.