The incident "The Fall of the Capital", on "May 23" in the year of At Dau (July 5, 1885), left a permanent mark on the spiritual life and spiritual activities of the people of the ancient capital of Hue. Every year, around the end of the 5th lunar month, the Ancient Capital prepares for worshiping ceremonies, in every family, every alley and corner of the street, to commemorate all those who have sacrificed, "died in battle", during the extremely tragic days of the Nguyen Dynasty's Imperial City. Recorded memories, personal recollections, and historical research continue one after another about the "May 23" event in Hue Citadel.