Is the Roman Pantheon a colossal sundial ?

Has the grand Roman Pantheon been keeping a secret for nearly 2000 years? An expert in ancient timekeeping thinks so, arguing that it acts as a colossal sundial.The imposing temple in Rome, completed in AD 128, is one of the most impressive buildings that survives from antiquity. It consists of a cylindrical chamber topped by a domed roof with an oculus in the top which lets through a dramatic shaft of sunlight. It boasts a colonnaded courtyard at the front."