Fatto generale: 90 is the latitude of the North Pole and the South Pole.
Fatto matematico: 90 is the number of degrees in a right angle.
Trivia: 90 is the number of minutes in a football (soccer) match.
Data storica: March 30th is the day in 1282 that the people of Sicily rebel against the Angevin king Charles I, in what becomes known as the Sicilian Vespers.