It is on Little Hagia Sophia Street and close to Marmara Sea. Building used as a mosque nowadays was a church built by Byzantine Emperor Justinian in between 531 and 536.
Little Hagia Sophia had served as a church for almost a thousand years, and converted into a mosque in 1506. Riwaq of portico at the north side of the structure, madrasah rooms around the small courtyard and a bath on the side street were added as a classical Ottoman architecture.
It is the form of irregular squares that outer walls are with a measure of 25×28 meters. There is an octagonal gallery wrapping the entire structure besides the altar notch. A fluctuating structure of dome appeared after being adapted to this octagon for not using any pendant on the dome covering the main venue. The dome is more than 15 meters in diameter and 19 meters high from the ground.
On the inscriptions covering the structure on the gallery floor it is written that Justinian built the church in the name of saints Sergius and Bacchus. On the column headers of both floors monograms of Justinian and his wife Theodora can be seen.