“All you can do is look,” says Mrs. Flowers. “The only solid thing in the Atlas is the ground. As I said, once the children try the newer things, they hardly ever come back.”

She leads Konstance toward the base of the wall. Everything is motionless. “Sooner or later, child,” Mrs. Flowers says, “all living things die. You, me, your mother, your father, everyone and everything. Even the limestone blocks from which these walls were constructed consist predominantly of the skeletons of long-dead creatures, snails and corals. Come.”

In the shadow of the nearest tower stand a few images of people: one looking up, another caught mid-climb along the stairs. Konstance can see a shirt with buttons, blue pants, a man’s sandals, a woman’s jacket, but the software has blurred their faces. “For privacy,” explains Mrs. Flowers. She points to a staircase winding round the tower. “We go up.”

“I thought you said the only solid thing is the ground.”

Mrs. Flowers smiles. “Wander around in here long enough, dear, and you’ll discover a secret or two.”

With each step up, Konstance can see more of the modern city sprawled around both sides of the old wall: antennas, automobiles, tarps, a building with a thousand windows, everything frozen in time; she can hardly breathe trying to take it all in.

“For as long as we have been a species, whether with medicine or technology, by gathering power, by embarking on journeys, or by telling stories, we humans have tried to defeat death. None of us ever has.”

They reach the top of the tower and Konstance gazes out, dizzy: the rust-red brick, the limestone made from the bodies of dead creatures, the green ivy flowing up the walls in waves—it’s all too much.

“But some of the things we build,” continues Mrs. Flowers, “do last. Around the year 410 of the Common Era, the emperor of this city, Theodosius the Second, began constructing these walls, four miles of them, to connect with the eight miles of sea walls the city already had. The Theodosian walls had an outer wall, two meters thick and nine high, and an inner one, five meters thick and twelve high—who can guess how many bodies were broken in their construction?”

A tiny insect has been captured crossing the railing directly in front of Konstance. Its carapace is blue-black and shiny, its legs incredible in their articulations: a beetle.