Helena, mother of Constantine the Roman Emperor, first marked this spot about 325 AD where it's believed Jesus Christ was born. Following her son's conversion to Christianity, Helena traveled to Palestine sites held sacred by the Christian world. The Church of the Nativity was later built over it in 530 AD, on the site of the ancient inn where Mary and Joseph stayed.
Luke 2:7
She gave birth to her first child, a son. She wrapped him snugly in strips of cloth and laid him in a manger, because there was no lodging available for them. (NLT)