The 120-year-old church located in the Balat district of Turkey's Istanbul was under restoration for seven years. Its original wooden structure was destroyed in a fire.
The leaders of Turkey and Bulgaria reopened the iconic Bulgarian St Stephen's Church in Istanbul on Sunday after seven years of restoration.
President Recep Tayyip Erdogan, Prime Minister Binali Yıldırım and Bulgarian Prime Minister Boyko Borissov attended the opening ceremony.
Erdogan said reopening of the Iron Church was an important message for the international community.
"I believe it is the responsibility of the state to ensure everyone can worship freely," he said, adding that Turkey has supported the restoration of more than 5,000 artefacts in the past 15 years.
The Bulgarian Orthodox church in Balat, a historic Istanbul neighbourhood on the shores of the Golden Horn traditionally home to Christians and Jews, was built in 1898 after its original wooden structure was destroyed in a fire.
Made out of cast iron, the iconic ornate building has been dubbed the "Iron Church."
The iron elements were produced in Austria in the 19th century and shipped to Istanbul through the Danube and the Black Sea.
TRT World's Aadel Haleem has more.
Ties between Bulgaria and Turkey had strained during recent years.
But in a show of co-operation, both countries co-funded St Stephen's restoration, one of the world's oldest prefabricated cast iron churches.
Turkish authorities funded 16 million Turkish lira while Bulgaria contributed one million Turkish lira for the church's restoration.
Turkey is home to more than 200,000 ethnic mostly Muslim Turks with Bulgarian passports who left Bulgaria during the communist era.
Around a third of them regularly turn out for Bulgarian elections, with the last ballot taking place on March 26.
Bulgaria, meanwhile, is home to a 700,000-strong ethnic mostly-Muslim Turkish minority, a legacy of the Ottoman empire.
Cuma Mosque in return
Vasil Liaze, president of a foundation overseeing the church, told Turkish media that the church had been restored under so-called rules of reciprocity.
This means that Sofia has given the green light for the Cuma (Friday) Mosque in Bulgaria's second city of Plovdiv to be restored in return.
Greek Orthodox mark Epiphany Day
In the meantime, the Greek Orthodox Christian community in Istanbul has celebrated Epiphany with the traditional blessing of the waters.
Ecumenical Patriarch Bartholomew I, the spiritual leader of Orthodox Christians around the world and the archbishop of Istanbul, led the liturgy on Saturday at the Patriarchal Church of St George located again in Balat district.
The Eastern Orthodox Church commemorates Jesus' baptism on Epiphany. Several blessings of the waters took place across Istanbul. The ceremony consists of a cross being tossed into the water to be retrieved by swimmers.
The patriarch threw the blessed cross into the waters of Istanbul's Golden Horn as the faithful jumped into the sea.
Nikos Solis, 29, a personal trainer from Greece, retrieved the wooden cross three years in a row.
Bartholomew presented Solis with a golden crucifix on a chain.