Istanbul's Bulgarian iron church dating back to the 19th century will be reopened Sunday after a seven-year renovation.

Located in Balat, the old Jewish quarter on the shore of Istanbul's Golden Horn, the Bulgarian Church of Sveti Stefan—known as the world's only surviving, completely-iron church—will be reopened with a ceremony to be attended by Turkish President Recep Tayyip Erdogan along with the Bulgarian Prime Minister Boyko Borisov.

Vasil Liaze, president of the Bulgarian Orthodox Church Foundation, said the opening ceremony will be a grand one and thanked all parties which have contributed to the restoration of the church.

He said thousands of believers from Bulgaria are expected to attend the ceremony.

An outstanding symbol of the Bulgarian Orthodox faith, the church was built in 1898 on the site of a wooden church destroyed in a fire. With its three domes and rich exterior decoration, the church stands out among many other Orthodox churches in Istanbul.

The prefabricated parts weighing some 500 tons were sent to Istanbul on small cargo ships from Vienna via the Danube, the Bosporus and the Golden Horn.

Its Armenian architect, Hovsep Aznavur, won a design competition organized by the then-Bulgarian authorities. The constructor was Rudolf von Wagner from Vienna.

Liaze said President Recep Tayyip Erdoğan initiated the restoration after a request from the Bulgarian minority in the city when he was serving as the prime minister.

"[Erdoğan] had already helped us when he was Istanbul mayor. We are also neighbors. He is from Kasımpasa, we're from Balat. We asked him about 8-9 years ago, and he ordered the restoration of the church," Liaze said.

He said each part, to the finest detail, was disassembled, repaired, then placed back in its original place.

"All the main columns were changed and the Iron Church was made to last for more than 100 years. We are sure it would be chosen as the most beautiful church in Istanbul," Liaze said.

Istanbul Metropolitan Municipality financed the restoration which cost 16 million Turkish liras (approx. $4 million). The Bulgarian government also contributed 1 million Turkish liras (roughly $253,000) to the project