The Christian Archaeological Society (ChAE), the academic society of the Greek researchers of Byzantine archaeology and art, founded in 1884, has maintained a continuing watch over the state of preservation of the Byzantine monouments in Constantinople (Istanbul), since the change of their legal status from museums to religious foundations in 2020. Hagia Sophia, perhaps the highest achievement of Byzantine architecture and art, and the Chora monastery, with the Palaiologan frescoes and mosaics, are now under circumstances that threaten their preservation.