It may have been around for 2000 years, but in all that time the purpose behind the Pantheon’s unusual design has never quite been understood, until now perhaps. Two researchers, including one from New Zealand, say the design might well have served as a sun dial, positioned to illuminate the building entrance just as the emperor was walking in. The Telegraph’s Nick Squires explains.
It is one of the best preserved buildings from the Roman world, a 2,000-year-old testament to the immense power and wealth of the empire.
But mystery has always surrounded what lies behind the unusual design of the Pantheon, a giant temple in the heart of Rome that was built by the Emperor Hadrian.
Now experts have come up with an intriguing theory – that the temple acted as a colossal sun dial, with a beam of light illuminating its enormous entrance at the precise moment that the emperor entered the building.
Constructed on Hadrian's orders and completed in AD128, the Pantheon's hemispherical dome is punctured by a 30ft-wide circular hole known as the 'oculus'.
It provides the interior of the building with its only source of natural light and allows in rain and – on rare occasions – snow.
Giulio Magli, a historian of ancient architecture from Milan Polytechnic, Italy, and Robert Hannah, a classics scholar from the University of Otago in New Zealand, have discovered that at precisely midday during the March equinox, a circular shaft of light shines through the oculus and illuminates the Pantheon's imposing entrance.