remains dating to the 5th century were found in tomb in hwangnam-dong .
show a man 's bones on top of a woman 's who was buried with jewellery .
experts believe silla dynasty-era tomb was built for a noblewoman and her lover or bodyguard was sacrificed and buried on top of her .
there 's a suggestion that the set-up may have been designed to show two people having sex - and the silla were known for their explicit pottery .