Rise of Chichen Itza
At the equinox a serpent of shadow slides down the pyramid

As the Classic Maya cities of the south emptied, Chichen Itza rose in the northern Yucatán. Its pyramid of Kukulcán is famous for the equinox, when shadows on its northern stairway form the body of a serpent. The city had Mesoamerica's largest ballcourt, about 168 metres long, and a sacred cenote into which offerings and victims were cast.
Wikipedia (Russian) · Wikipedia (English) · 9th century
Meanwhile around the world (±25 years)
Eastern Europe & Russia
- 882 Oleg takes Kiev — 18 years earlier
- c. 895 Hungarian conquest of the Carpathian Basin — 5 years earlier
Africa
- c. 900 The bronzes of Igbo-Ukwu — same year
Alive at the time
- Oleg the Wise (aged 55)
- Igor of Kiev (aged 22)
- Æthelstan (aged 6)
- Edward the Elder (aged 26)