His head bowed and hands clasped in front of him, Pope Francis stood today for two minutes of silent prayer facing east inside one of Istanbul's most important mosques, as he shifted gears toward more religious affairs on the second leg of his three-day visit to mainly Muslim Turkey.
Following in the footsteps of Pope Benedict XVI who visited Turkey in 2006, Francis prayed alongside the Grand Mufti of Istanbul, Rahmi Yaran, who had his palms turned toward the sky in a Muslim prayer, inside the 17th-century Sultan Ahmet mosque.
"May God accept it," Yaran told the pope at the conclusion of a poignant moment of Christian-Muslim understanding.
The Vatican spokesman, Rev Federico Lombardi called it a moment of "silent adoration". Lombardi, who was standing behind the pope, said Francis told the mufti twice that we must "adore" God and not just praise and glorify him.
It was a remarkably different atmosphere from Francis' first day in Turkey, when the simple and frugal pope was visibly uncomfortable with the pomp and protocol required of him for the state visit part of his trip.
With president Recep Tayyip Erdogan's mega-palace, honour guard and horse escort now behind him, Francis got down to the business of being pope, showing respect to Muslim leaders, greeting Istanbul's tiny Catholic community and later meeting the spiritual leader of the world's Orthodox Christians.
Francis nodded, smiled and looked up in awe as Yaran gave him a tour of the Blue Mosque, famed for its elaborate blue tiles and cascading domes. Francis listened intently through an interpreter as Yaran explained verses of the Muslim holy book.
Presenting the pope with a blue, tulip-designed tile, Yaran said he prayed to God that his visit would "contribute to the world getting along well and living in peace".
"We are in need of prayers. The world really needs prayers," Yaran said.
Benedict had visited Turkey amid heightened Christian-Muslim tensions and prayed at the mosque in a gesture of respect for Islam that was appreciated by many Turks. The Vatican added the stop at the Blue Mosque at the last minute to show Benedict's respect for Muslims.
The Vatican also acted to avoid offence to its Muslim hosts by moving up Francis' visit to the mosque so it wouldn't coincide with noon prayers.
After he left, Francis walked a short distance - greeting crowds for the first time in his visit - to tour the nearby Haghia Sophia, which was the main Byzantine church in Constantinople - present-day Istanbul - before being turned into a mosque following the Muslim conquest of the city in 1453. The Haghia Sophia is now a museum, although some Islamic groups want it to be converted back into a mosque.
Pope Paul VI, who made the first papal visit to Turkey in 1967, fell to his knees in prayer inside Haghia Sophia, triggering protests by Turks who claimed Paul had violated the secular nature of the domed complex. Francis avoided any religious actions inside.
Halfway through his tour, the Muslim call for prayer echoed off the Haghia Sophia's marble walls, an evocative moment that symbolised the crossroads of East and West that Istanbul represents.
Museum director Hayrullah Cengiz pointed to a niche with a Byzantine fresco of the Virgin Mary holding an infant Jesus, saying it was his favourite corner because the area also features Arabic writings of the names of the Prophet Mohammed and Allah.
"They are all together," Cengiz said.
A few dozen well-wishers outside Haghia Sophia waved a combination of the Turkish and the flag of the Holy See. One carried a banner that read: "You are Peter."
Francis nearly tripped over while walking along the carpet from his plane to a VIP terminal at Istanbul's Ataturk Airport. The governor of Istanbul and Patriarch Bartholomew I, the spiritual leader of Orthodox Christians, helped the pontiff as he tottered.
Later today Francis will meet Bartholomew, the real reason for his visit to Turkey.
The two major branches of Christianity represented by Bartholomew and Francis split in 1054 over differences on the power of the papacy. The two spiritual heads will participate in an ecumenical liturgy and sign a joint declaration in the ongoing attempt to reunite the churches.