Which Byzantine church in Istanbul was originally built as the Church of Saints Sergius and Bacchus?

The Byzantine Church of Saints Sergius and Bacchus in Istanbul is now known as Little Hagia Sophia.

The church was built in Constantinople during the reign of Emperor Justinian I, probably between 527 and 536, and was associated with Justinian and Empress Theodora. Its dedication honored Saints Sergius and Bacchus, Roman soldiers who were venerated as Christian martyrs.

The building has a distinctive octagonal central space enclosed within a roughly rectangular structure. Its dome rests on an octagonal arrangement of supports, creating an interior that differs from the larger Hagia Sophia while showing related experimentation with centralized planning.

The modern nickname reflects architectural similarities and its proximity in historical memory to Hagia Sophia. It should not be confused with Hagia Eirene, the Church of Divine Peace, another major Byzantine church in Istanbul.