Rome is preparing for hundreds of thousands of pilgrims and dozens of foreign delegations visiting the Vatican on Sunday for the double canonisation of popes John Paul II and John XXIII.
Italy's interior ministry said it was expecting 19 heads of state, 24 heads of government and 800,000 pilgrims.
"It will be an event of global significance," Rome mayor Ignazio Marino said in the run-up to the ceremony that will confer sainthood on the two late pontiffs.
Monsignor Liberio Andreatta, head of the Vatican agency for pilgrims, said: "This is an event that Rome has never seen in its history, the canonisation of two popes in the presence of two living popes".
Pope emeritus Benedict XVI, who last year became the first pontiff since the Middle Ages to step down, was expected although the Vatican said the elderly ex-pope had not yet decided whether he would attend.
Rome city hall said authorities had put in place a €7.8 million (HK$83.5 million) plan for increased visitors that began before Easter and will run until May 1.
For the period of the canonisation, the city's plan is to boost public transport with extra buses on Saturday and Sunday and run the metro system around the clock.
Also, 19 giant screens are being set up around the city to follow the ceremonies in multiple languages including Arabic, French, Italian, Polish and Spanish.
The mayor's office is expecting 4,300 buses and there were will be special trains and flights to the city. Some pilgrims will even arrive by boat to the port of Civitavecchia near the capital.
"From Poland alone, we are expecting 1,700 coaches, 58 charter flights and five special trains," said Maurizio Pucci, an official from Rome city hall, saying the canonisation would put the city under "stress".
The interior ministry will use 2,400 security officers and there will be about 2,000 extra police in the streets in anticipation of a crime surge.
- An Italian man was crushed to death by a giant crucifix honouring John Paul II that collapsed during a ceremony ahead of the late pope's canonisation.
A piece of the 30-metre high wooden cross fell during Wednesday's event near an Alpine village, killing the young man, who was in his early 20s, on the spot, Italian media reported yesterday.
The Jesus Christ statue on the cross is six metres high and weighs 600kg and the crucifix was curved and fixed to the ground with cables, the reports said.
The cross was designed by sculptor Enrico Job and was created for John Paul II's visit to Brescia in the Lombardy region in northern Italy in 1998.