Hagia Theodosia Church (Gul Mosque) in Istanbul

Hagia Theodosia Church is one of the most important stops on my walking tour covering Cibali, Fener and Balat districts. The building, which is essentially a 1000-year-old church from the Byzantine period, is today known as the Gul Mosque.

St Theodosia was an iconophile woman who was killed by Roman soldiers during the Byzantine iconoclasm. When the period of anti-iconism, which lasted about a century, ended, the Eastern Church declared this woman a martyr and saint.

The Byzantines built this church in the 11th century in honor of this female saint who was believed to heal people. The building remained a church for about 500 years, and was converted into a mosque after the Ottomans captured Constantinople.

In this article, I would like to briefly share with you a few important information about Hagia Theodosia Church. If you would like to explore this thousand-year-old unique structure and hear the stories associated with it, you can also join my private Fener and Balat walking tours.

Church of Hagia Theodosia (Gul Mosque)

Hagia Theodosia Church a Byzantine Structure now Gul Mosque

Hagia Theodosia Church was a Byzantine building with a Greek cross plan, believed to have been built in the 11th century. The building, which has a very high dome, served as a church for nearly 500 years.

With the Ottoman conquest of Istanbul in 1453, the churches in the city were converted into mosques one by one. It is believed that this church was also converted into a mosque in the 1490s. The name of the mosque is interestingly given as Gul Mosque, which means “The Rose Mosque”.

It is believed that the reason why the mosque took this name was that when Ottoman soldiers entered the city, they found the old church decorated with roses. The reason was that the day the city fell on May 29, 1453 coincided with St. Theodosia’s feast day, and that’s why the church was decorated with flowers.

Although the church is very similar to its original form, it has not survived to the present day as it was during the Byzantine period, because it was partially damaged by the earthquakes in Istanbul over time.

The Ottomans repaired the dome of the building and the arches supporting it and added a little of their own style to the architecture. This mixed architecture can be quite interesting to eyes that examine it carefully.

Another interesting detail about this building is that large Stars of David can be seen on some of the main supporting columns and arches in the interior decoration that was renewed during the Ottoman period.

How to Visit Gul Mosque Today?

Gul Mosque (former Hagia Theodosia Church) is located very close to Kadir Has University, the iconic building in Cibali today. You can easily find this spot as the university is on the banks of the Golden Horn and on the main road.

From the university, you can walk along the seashore, parallel to the old Roman walls, and when you come to Serefiye Street, you can see the church by heading southwest on this street. To do this, you need to take the sea (i.e. the Golden Horn) behind you and start walking through this side street.

Since the church is built on a hill, it is impossible to miss. Like every Byzantine structure, its distinguishing feature is that it is made of red bricks, which are easily visible from the outside.

Although the mosque is open for Muslims to pray during worship, it is not open to visitors all day long, like the Blue Mosque and Suleymaniye Mosque in the tourist spots of the Old City.

If the mosque official is there, when you ask, he will open the door of this castle-like building and allow you a 10-minute visit. However, please do not forget to give him a reasonable tip in return for this kindness.

An interesting detail is that the mosque has a giant wooden door with two wings and this door is opened with a huge old-style key that resembles a castle key. As you can see, this place is truly a hidden treasure for history lovers.


Gul Mosque, or formerly known as Hagia Theodosia Church, is a little-known hidden gem among the Byzantine structures in Istanbul, but it impresses visitors with its mystical atmosphere.

If you visit this area with an expert tour guide, you can discover this structure and many other hidden treasures. Gul Mosque, the nearby St Nicholas Church and the St Mary of the Mongols Church in Fener are places that the average tourist will never see.

As someone who has been organizing private tours in Istanbul for nearly 20 years, I have been doing the Fener and Balat tour since 2008. Many foreign tourists have participated in this private guided walking tour and have written their impressions on this page.

In this walking tour, we leave Istanbul’s classic tourist route and explore places off the beaten path. Cibali, Fener and Balat, some of the most cosmopolitan districts of the Ottoman period, have many unique stories.

Fener was a Greek district and Balat was a Jewish district during the Ottoman period. Traces of cosmopolitan life in these districts can still be clearly seen through mosques, churches and synagogues.

If you would like to discover the hidden treasures offered by these unique districts, you can book my private guided Fener and Balat tour. In order to contact me, please simply fill out the form on the contact page.

Writen by Serhat Engul

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