The so-called “Cistern of Theodosius” (Turkisk Şerefiye Sarnıcı) lies a short distance southeast of the Forum of Constantine, west of the so-called “Cistern of Philoxenos”. The cistern, which is made of brick lined with hydraulic mortar, is around 24x40 meters. Its roof consists of a series of brick vaults, supported by 32 marble columns (4 rows of 8 columns) with Corinthian capitals and impost blocks. It seems to date to the 5th century.

While it is often identified as the Theodosius Cistern, it was located in the Fifth Region of Constantinople, which was located northeast of this cistern. Other cisterns are known to have been in the vicinity, such as the Cisterna Maxima said to be located near the Forum of Constantine. It opened in 2018 after undergoing restoration for several years.