The 'mystery' is Gobekli, the (disappeared for me) article is backed up here:<p><a href="https://web.archive.org/web/20210815221449/https://www.bbc.com/travel/article/20210815-an-immense-mystery-older-than-stonehenge" rel="nofollow">https://web.archive.org/web/20210815221449/https://www.bbc.c...</a>