The Large Structure

They spent forty minutes documenting from inside the Pip.

Mara worked the cameras systematically, moving from one end of the plateau to the other in slow passes, capturing every structure from multiple angles. Sol worked the instruments, logging depth readings and water temperature and the exact coordinates of everything they could see, his notebook open on his knee, writing down observations in the small neat handwriting he used when he was concentrating hard.

The structures became more interesting the longer she looked at them.

The smaller ones, the rounded buildings that covered most of the plateau, had openings in them that were too regular to be accidental damage. Doorways, she thought, though she did not say it out loud because saying it out loud made it feel too large. The walls of the ones that had partly collapsed showed layers of different materials, as though they had been repaired and modified over time. Several of them had markings on their outer surfaces, patterns that were too deliberate to be weathering but too worn to make out clearly.

The large structure at the far end was the one she kept coming back to.

It was at least four times the height of the others, its walls still mostly intact, its outline clear against the pale rock of the plateau behind it. The carved detail she had noticed from further away was, up close, unmistakably intentional. Geometric patterns covered the lower half of the walls, precise and repeating, the kind of pattern that took skill and planning to create.

And at the very centre of its front face, directly above what could only be described as an entrance, was a circular symbol about a metre across. Inside the circle, carved in deep relief, was a shape that made Mara stop moving the cameras entirely.

It was a wave. Stylised, simplified, but unmistakably a wave. Above it, also inside the circle, was a shape that might have been a hand, or might have been something else, reaching upward toward the surface of the water.

"Sol," she said.

"I see it," he said. He had been looking at the same thing.

"The wave," she said. "Reaching upward."

"Toward the surface," he said. "Yes."

They were quiet for a moment. The Pip hummed softly around them. Outside the porthole the city sat in its green water, still and patient and full of things they did not yet understand.

"They knew about the surface," Sol said. "Whoever built this. They knew there was something above the water."

"Or they came from the surface," Mara said. "Once. A very long time ago."

Sol wrote something in his notebook. Then he looked at her. "We need to go and get Mum," he said.

"Yes," Mara said. "Right now."

She took three more camera passes over the large structure, the symbol, the entrance, the carved walls. Then she powered up the Pip's ascent and they rose slowly through the clear green water, the plateau shrinking below them, the structures becoming smaller and then hazier and then invisible as the light changed and the ordinary blue of the deeper water closed over it.

She felt, as it disappeared from view, a strong urge to go back down immediately. The city had been down there for an enormously long time. It was not going anywhere. But knowing that did not make the urge any smaller.

She resisted it. Mum first. Everything else after.