Located along the shore of the Golden Horn in Fatih, Turkey, the Bulgarian Church of St. Stephen is no ordinary basilica. Unlike most churches of its time, St. Stephen’s is constructed entirely out of cast iron, explains Atlas Obscura in their article "Bulgarian Iron Church." This method of construction was cost-effective and efficient for the time, but never became popular.
According to urban legend, in an effort to thwart construction efforts, Sultan Abdulaziz only permitted the building of a Bulgarian Orthodox church if it could be built within one month. While the building of the church was quick, one month would not have been enough time to pour 500 tons of iron slabs in Vienna, float them down the Danube River, across the Black Sea, through the Bosporus, and then assemble them on-site. In reality, St. Stephen’s was a part of a design competition funded by the Bulgarian government.
Learn more about the church in the full article on Atlas Obscura, here.