St. Antoine Church
Time Out says
The largest and most prominent Catholic church in Istanbul, the majestic St. Antoine on Istiklal Caddesi was built between 1906 and 1912 in the Venetian Neo-Gothic style. St Antoine offers masses throughout the week in English, Turkish, Polish and Italian, and is a nice place to pop in for a moment of silent reflection after spending the morning traversing the crowded Beyoğlu district. Before being elected as pope, Pope John XXIII preached at St. Antoine for a number of years when he served as Vatican's apostolic delegate to Turkey. He is commemorated by a statue located in the courtyard.