BBC - Pope Leo XIV has visited Istanbul's Sultan Ahmed Mosque - widely known as the Blue Mosque - in his first visit to a Muslim place of worship since he took up the papacy in May.
The Pontiff was seen bowing as he entered the building, but it is reported he did not pray at the mosque, as his two predecessors had done.
The Vatican said in a statement Leo undertook the tour "in a spirit of reflection and listening, with deep respect for the place and for the faith of those who gather there in prayer".
The Pope is on a four-day trip to Turkey, after which he will visit Lebanon.
He was later welcomed to St George's Cathedral in Istanbul by the head of the Eastern Orthodox Church, Patriarch Bartholomew.
The Blue Mosque is officially named for Sultan Ahmed I, leader of the Ottoman Empire from 1603 to 1617, who oversaw its construction.
It is decorated with thousands of blue and turquoise ceramic tiles and receives millions of visitors each year.
Pope Francis prayed there in 2014, and Pope Benedict XVI did so in 2006.
The first pope to officially enter a mosque was John Paul II, who made history when he visited the Umayyad Mosque in Damascus in 2001.
The papal visit to Turkey and Lebanon had been planned by late Pope Francis, but its theme of building bridges was embraced by Pope Leo from the moment he stepped on the balcony of St Peter's Basilica after his election in May.
At the start of his trip, he warned that the world should not give into "a heightened level of conflict on the global level", adding that "the future of humanity is at stake".
In Lebanon - where an estimated third of the country is Christian - he is expected to meet more faith leaders and hear from young people.
On the final day of the trip, he will celebrate Mass at the Beirut waterfront at the site of the 2020 port explosion, praying for the more than 200 people who were killed and 7,000 others injured.