In by the waters of Babylon what is the irony?

In "By the Waters of Babylon," the irony lies in the protagonist's journey to seek knowledge about the "dead" civilization, which he initially believes to be a place of danger and forbidden. He discovers that the ruins of the "gods" are remnants of a once-great society, filled with advanced technology and wisdom, contrasting sharply with the superstitions and fears held by his own people. This irony highlights the theme of knowledge versus ignorance, as the protagonist learns that the past civilization's downfall was partly due to their own hubris and misuse of power. Ultimately, the irony underscores the cyclical nature of civilization and the lessons that can be gleaned from history.