Pope Benedict XVI greets faithful from his summer residence of Castel Gandolfo, the scenic town where Pope Benedict XVI will spend his first post-Vatican days and made his last public blessing as pope,Thursday, Feb. 28, 2013. AP Photo/Luca Bruno Vatican Swiss guards close the main door of the papal residence in Castel Gandolfo, south of Rome, Thursday, Feb. 28, 2013. Benedict XVI greeted the faithful for the last time as pope on Thursday, telling tearful well-wishers that he is beginning the final stage of his life as "simply a pilgrim," hours before he becomes the first pontiff in 600 years to resign. In this image taken from video as Pope Benedict XVI deliveres his final greetings to the assembly of cardinals at the Vatican Thursday Feb. 28, 2013, before he retires in just a few hours. Benedict urged the cardinals to work in unity and promised his "unconditional reverence and obedience" to his successor in his final words to his cardinals Thursday in a poignant and powerful farewell before he becomes the first pope in 600 years to resign. AP Photo/Vatican TV In this image taken from video as Pope Benedict XVI, seated at centre, delivered his final greetings to the assembly of cardinals at the Vatican Thursday Feb. 28, 2013, before he retires in just a few hours. In this image taken from video as Pope Benedict XVI enters to deliver his final greetings to the assembly of cardinals at the Vatican Thursday Feb. 28, 2013, before he retires in just a few hours. CASTEL GANDOLFO, Italy (AP) - Benedict XVI left the Catholic Church in unprecedented limbo Thursday as he became the first pope in 600 years to resign, capping a tearful day of farewells that included an extraordinary pledge of obedience to his successor. As bells tolled, two Swiss Guards standing at attention at the papal palace in Castel Gandolfo shut the thick wooden doors shortly after 8 p.m., symbolically closing out a papacy whose legacy will be most marked by the way it ended - a resignation instead of a death. Benedict, who will spend his first two months of retirement inside the palace walls, leaves behind an eight-year term shaped by struggles to move the church beyond clerical sex abuse scandals and to reawaken Christianity in an indifferent world - efforts his successor will now have to take up. For the time being, the governance of the Catholic Church shifts to Cardinal Tarcisio Bertone, the camerlengo, or chamberlain, who along with the College of Cardinals will guide the church and make plans for the conclave to elect the 266th leader of the world's 1.2 billion Catholics. One of Bertone's first acts was to lock the papal apartment inside the Vatican. In another task steeped in symbolism, he will ensure that Benedict's fisherman's ring and seal are destroyed. On Benedict's last day, the mood was vastly different inside the Vatican than at Castel Gandolfo. At the seat of the popes, Benedict's staff tearfully bade the pontiff good-bye in scenes of dignified solemnity. A more lively atmosphere reigned in the countryside, with well-wishers jamming the hilltop town's main square shouting "Viva il Papa!" (Long live the pope!) and wildly waving the yellow and white flags of the Holy See. "I am simply a pilgrim beginning the last leg of his pilgrimage on this Earth," Benedict told the cheering crowd in his final public words as pope. It was a remarkable bookend to a papacy that began on April 19, 2005 with a similarly meek speech delivered from the loggia overlooking St. Peter's Square, where the newly elected Benedict said he was but a "simple humble worker in the vineyard of the Lord." Over eight years, Benedict tried to set the church on a more traditional course, convinced that all the ills afflicting it - sexual abuse, dwindling numbers of priests and empty pews - were a result of a misreading of the reforms of the Second Vatican Council. His successor is likely to follow in his footsteps given that the vast majority of the 115 cardinals who will elect the next pope were appointed by Benedict himself and share his conservative bent. For the most part, his cardinals have said they understood Benedict's decision. But Sydney Cardinal George Pell caused a stir on Thursday by saying it was "slightly destabilizing" - a rare critique of a pope by one of his cardinals. Benedict's journey into retirement began with a final audience with his cardinals Thursday morning, where he sought to defuse concerns about his future role and the possible conflicts arising from the peculiar situation of having both a reigning pope and a retired one living side-by-side inside the Vatican. "Among you is also the future pope, whom I today promise my unconditional reverence and obedience," Benedict told the cardinals. Benedict's decision to live at the Vatican in retirement, be called "emeritus pope" and "Your Holiness" rather than revert back to "Joseph Ratzinger" and wear the white cassock associated with the papacy has deepened concerns about the shadow he might cast over the next papacy. Benedict has tried to address those worries over the past two weeks, saying that once retired he would be "hidden from the world" and living a life of prayer. On Thursday he took a step further with his own public pledge to place himself entirely under the authority of the new pope. Benedict also gave a final set of instructions to the "princes" of the church who will elect his successor, urging them to be united as they huddle to choose the next pope. "May the College of Cardinals work like an orchestra, where diversity - an expression of the universal church - always works toward a higher and harmonious agreement," he said. It was seen as a clear reference to the deep internal divisions that have come to the fore in recent months following the leaks of sensitive Vatican documents that exposed power struggles and allegations of corruption inside the Vatican. The audience inside the Apostolic Palace was as unique as Benedict's decision to quit, with the pope, wearing his crimson velvet cape and using a cane, bidding farewell to his closest advisers and the cardinals themselves bowing to kiss his fisherman's ring for the last time. A few hours later, Benedict's closest aide, Monsignor Georg Gaenswein, wept by his side as they took their final walk down the marbled halls of the Apostolic Palace to their motorcade that took them to the helipad at the top of a hill in the Vatican gardens. As bells tolled in St. Peter's and in church towers across Rome, Benedict took off in a helicopter that circled St. Peter's Square, where banners reading "Thank You" were held up skyward so he could see. He flew to Castel Gandolfo, where he has spent his summers enjoying the quiet gardens overlooking Lake Albano. Around the time he took off, the Vatican sent a final tweet from Benedict's Twitter account, (at) Pontifex. Thank you for your love and support. May you always experience the joy that comes from putting Christ at the centre of your lives. Soon afterward, that tweet and all Benedict's previous ones were deleted and the profile was changed to read "Sede Vacante." And a few seconds past 8 p.m., the soft click of the 20-foot-high wooden door at Castel Gandolfo closed, signaling the end of the papacy. A Vatican official was then seen taking down the Holy See's white and yellow flag from the Castel Gandolfo residence. "We have the pope right here at home," said Anna Maria Togni, who walked two kilometers (one mile) from the outskirts of Castel Gandolfo to witness history. We feel a tenderness toward him. Benedict set his resignation in motion Feb. 11, when he announced that he no longer had the "strength of mind and body" do to the job. It was the first time that a pope had resigned since Pope Gregory XII stepped down in 1415 to help end a church schism. In the weeks since Benedict's announcement, speculation has mounted whether other factors were to blame. By the time his final day came around though, Benedict seemed perfectly serene with his decision. The Vatican spokesman, the Rev. Federico Lombardi, said the pope's pledge to obey his successor was in keeping with his effort to "explain how he intends to live this unprecedented situation of an emeritus pope." "He has no intention of interfering in the position or the decisions or the activity of his successor," Lombardi said. But as every member of the church, he says fully that he recognizes the authority of the supreme pastor of the church who will be elected to succeed him. The issue of papal obedience is important for Benedict. In his last legal document, he made new provisions for cardinals to make a formal, public pledge of obedience to the new pope at his installation Mass, in addition to the private one they traditionally make inside the Sistine Chapel immediately after he is elected. The Rev. Thomas Reese, author of "Inside the Vatican," a guide to the Vatican bureaucracy, welcomed Benedict's similarly public pledge, saying: "There is room in the church for only one pope and his pledge of obedience shows that Benedict does not want to be used by anyone to undermine the authority of the new pope." He said he would have preferred Benedict to go back to his given name and eschew the white of the papacy. "Symbols are important in the church," he said. Winfield reported from Vatican City. Follow Nicole Winfield at www.twitter.com/nwinfield