“At this point, just about the only thing it means to be Iraqi is that you are responsible for the civilization that was here and goes back thousands of years, nothing else,” Mr. Dawood added.

His friend Muyaed Albassam, 65, said: “Culture is a tool to reunite us. Although what can it mean in the midst of murder and sectarianism?”

“I’ll tell you,” Mr. Albassam answered himself. “When Iraqis see life in the rest of the world, we feel we are poor, worthless. We are No. 1 only in corruption. But we have this past, as the source of civilization.”

Several young men were clustered on a different bench across the room, smoking hookahs. “It is our identity, our heritage, yes,” Abbas Jabir, 25, said, “but a generation has grown up since 2003 that isn’t educated in this history, in this idea of national pride, and so is more susceptible to ISIS.”

Ahmed Khaled, 28, agreed: “We lost our history. We need to spread this message about culture as a thing that unifies us — if it is not too late.”

But which culture?

That same day, Haider Fadhil, 21, was hanging out with friends in the leafy courtyard of a partly demolished municipal building along the Tigris, enjoying the shade of a tall clock tower. Armed guards at the entrance frisked families coming there to picnic and sunbathe in peace.

“The reopening of the museum means Iraq is not without hope,” Mr. Fadhil said. “Our history can bind us together, although for me, to be Iraqi now mostly means to have lived under Saddam, through wars, with sectarianism, to have lost friends and family — yet to persist.”