The Solemnity of Saints Peter and Paul honors the martyrdom of Saint Peter and Saint Paul. Prior to the reforms of the calendar the feast was listed as a Double in the Tridentine Calendar, Double of the First Class in the Calendar of 1954 and a First-Class feast in the Calendar of 1960. In many dioceses the day is a Holy Day of Obligation (The United States and Canada do not list it as an obligatory day but the United Kingdom does). There is evidence from at least the year 258 showing that the day was celebrated to honor the martyrdom of both Saints.
In many Catholic-majority countries the day is celebrated as a public holiday and the city of Rome in particular celebrates the day as the two Saints are the patron saints of the Eternal City of Rome. In Rome all schools, banks, and Vatican city are closed. The Pope traditionally holds a special Mass in which he gives a pallium to archbishops who have been appointed during the previous year. The statute of Saint Peter is decorated with a rich red robe, rings and a crown and the evening holds a special fireworks show.
In Eastern Orthodoxy the feast marks the end of the Apostle's Fast and is one of five ranked as a great feast in the tradition with an all-night vigil starting the night before. The Coptic and Ethiopian Orthodox Tewahedo Church celebrate the feast on 5 Epip with the day also marking the end of the Apostle's fast.
Saint Peter was martyred in the year 64 AD in the circus of Nero via crucifixion as he was not a citizen of Rome. He famously requested to be crucified upside down believing himself not to be worthy of being killed in the same manner of Christ. Saint Paul, being a Roman citizen was martyred via beheading. Tradition that holds that his head bounced three times with a spring of water erupting from the ground where the head touched each time.