BROOKLINE -- Coming together to pray for Christian unity, Cardinal Seán P. O’Malley and Greek Orthodox Metropolitan Methodios led a joint prayer service Sept. 6.

The prayer service, celebrated in the chapel of the Greek Orthodox Metropolis, was held in preparation for a joint Catholic-Orthodox pilgrimage which will be led by Boston’s Catholic and Greek Orthodox spiritual leaders. In attendance were many of the nearly 100 Catholic and Orthodox pilgrims who will make the trip. They came to receive a pre-pilgrimage blessing and to meet Cardinal O’Malley and Metropolitan Methodios as well as their fellow travelers.

Departing from Boston on Sept. 16, the group will begin a 10-day journey to Rome, Istanbul and St. Petersburg, Russia.

Highlights are intended to include a general audience with Pope Benedict XVI, great vespers with the Patriarch Bartholomew of Constantinople, tours of the Vatican and Byzantine mosaics of Rome; the Hagia Sophia and Grand Bazaar in Istanbul; the shuttered orthodox seminary on the island of Halki; and, in Russia, the Hermitage Museum and the Orthodox churches of St. Petersburg.

In his homily at the prayer service Cardinal O’Malley spoke of the importance of the upcoming journey.

“For us this pilgrimage has such a special meaning because, as Catholic and Orthodox, we think back to the first millennium when our churches were one and we long for the day when once again we will have that same unity which we enjoyed in our origins,” the cardinal said.

“This pilgrimage -- where we come together in friendship and faith to pray together, to visit these holy places, to enjoy one another’s friendship and encourage each other -- is a wonderful opportunity and a great responsibility,” he continued.

According to Vito Nicastro of the archdiocese’s Office of Ecumenical and Interreligious Affairs, the pilgrimage builds on decades of close ties between Boston’s Catholic and Orthodox communities and follows a similar pilgrimage led by Metropolitan Methodios and Cardinal Bernard Law in October 1996.

“The Pilgrimage points to a deep-rooted decades-long relationship including all sorts of visits, common witness, collaboration for good, and theological dialogue,” Nicastro said. “For years we have practiced standing together, speaking together, praying together. We have been present for each others’ Easter week services, mirrored the exchange of delegations on feast days between Rome and Constantinople, and built relationships between our seminarians and our bishops.”

Nicastro also expressed the hope that the Boston experience of Catholic-Orthodox dialog will serve as an example for the wider Christian world.

“We have relentlessly sought to go deeper in love, build more trust, never satisfied until the day the goal [of Christian unity] will be met. We hope this relationship which has been truly one of the treasures of our churches can provide leadership, moving us all forward.”