One of the most iconic buildings in the world, the Pantheon in Rome is an enduring testament to the power and glory of ancient Rome.  At the same time, it has also always posed something of a mystery.  The only source of natural lighting is a thirty-foot diameter hole at the very top of the hemispherical dome, often referred to as the "oculus".

Working since 2009, scholars Guilio Magli and Robert Hannah discovered that at midday on the equinoxes, a shaft of circular light shines through the oculus and illuminates the Pantheon's entrance. 

[photo credit: Andrew Caswell and
Robert Cockburn of The Daily Telegraph ]

Ask a person what is the earliest evidence of humans building structures to mark significant celestial events, and one offer "Stonehenge".  But there may be a structure built thousands of years early according to some experts in Australia.

A site "down under", name Wurdi Youang, estimated to be older than 10,000 years, has a strange arrangement of stones with alignments toward solstices and equinox that has been scrutinized by several eminent Australian scientists.  They conclude that the placement and alignment of the stones is not an accident and there is a perfect alignment with the setting sun on the mid-summer day. Understandably, the exact location of the site is a well-guarded secret, but it is known to be west of Melbourne approximately 80 kilometers.