Small St. Sofia Mosque is located between Cankurtaran and Kadırga quarters in Eminönü District, 20 km away from the southern seaside of Mediterranean ramparts. Although it is stated in some sources that there was a pavilion of Big Palace, which is known as Hormidas Palace, and a basically planned church established for Apostle Petrous and Pavlos near Small St. Sofia Mosque, there is no proof which determines their exact locations.

Small St. Sofia Mosque or Ss. Sergius and Bacchus church with its former name, which is the useable oldest structure of İstanbul today, was constructed between the years 527-536. According to the legends stated in the sources about the construction of the building (Millingen 1912), at the 1st Anastasyus Period, 1st Justiniaunus and his uncle 1st Justinos were condemned to death due to an allegation that they had a rebellion against the Emperor Anastasyus.

One night before the execution, the Emperor Anastasyus sees the saints Ss. Sergius and Bacchus in his dream and the saints testifies in favour of 1st Justiniaunus and 1st Justinos. The emperor, who is affected by this dream, forgives them. When 1st Justiniaunus becomes emperor, he establishes Ss. Sergius and Bacchus church as a vow church in order to show his gratitude to these saints.After the conquer of İstanbul, the building, which was used as a church for nearly 1000 years, was changed to

a mosque by Hüseyin Agha, theKapu Agha, in 1504 during the 2nd Bayezid period.