The Blachernae Baths (Region XIV) were built in the late 6th century by Tiberius II and Maurice, though later mistakenly attributed to Leo I. Cedrenus (12th century) places them in the "Carian portico," while Pseudo-Codinus/Patria credits Basil II with their restoration. Yegül suggests they were part of the Blachernai Palace complex, near the Theotokos Church.

The Patria also mentions a "sacred bath" (hagion loutron) in Blachernae, possibly referring to these public baths or the hagiasma of Theotokos Blachernai. According to Yegül, the baths played a central role in a weekly imperial ritual: on Fridays, the emperor would arrive at Blachernae harbor, attend a ceremony at the basilica, don a ceremonial costume at the Triconchos, pray, and then bathe in the sacred pool three times before a reception.

Location implies that Blachernai was supplied by the Hadrian Waterway.

See further Bayülgen & Saner, 2024, p. 363-365 (substructures at Blachernai, look for possible identification?)

The confusion of the "holy bath" (hagion louma) could be explained by the authors mixing up the public bath with the spring in Theotokos Blachernai (which also includes Leo I in its history). Or, as the ritual implies, the emperor made use of both.