
1) Ancient Roman festival
Found on
https://www.crosswordclues.com/clue/decennalia

Decennalia (or decennia, from Latin decennium - `tenth anniversary`; decem, `ten` + annus, `year`) were Ancient Roman festivals celebrated with games every ten years by the Roman emperors. This festival owed its origin to the fact that in 27 BC, Augustus refused the supreme power offered to him for life. Instead, he would only consent to acc...
Found on
http://en.wikipedia.org/wiki/Decennalia

Decennalia were festivals instituted by Augustus in 17 BC, and celebrated by Roman emperors every ten years of their reign with sacrifices, games and largesses.
Found on
http://www.probertencyclopaedia.com/browse/OD.HTM
No exact match found.