The location of this cistern has not been identified yet. Possibly built by Stephen the Parakoimomenos under Maurice (r. 582-602). Possibly related to the 'bath' mentioned in the Patria (see source under 'Construction').
Altuğ, 2013, p. 51 states it was close to Unkapanı (today the road between Atatürk Köprüsü and Zeyrek/Bozdoğan Kemeri). This would roughly correspond with Region X.