“There is,” Treya said tersely. “A sort of bridge. We ought to be able to see it from here.”

She got down on her belly and scooted to the edge of the cliff, motioning for me to do the same. Heights don’t bother me particularly—I had flown airplanes for a living in the world before this one—but inching over that vertical drop wasn’t the most comfortable thing I had ever done. “Down there,” Treya said, pointing. “Do you see it?”

The sun was sinking and the chasm was already in shadow. Seabirds nested where centuries of wind and rain had carved hollows in the obdurate, artificial rock. Far to the left, I could see what she was pointing at. An enclosed tunnel connected this artificial island to the next, though only the far end of it was visible around the precise curvature of the island’s wall. The tunnel was a salt-rimed shade of black, the same color as the sea below. Vertigo and the odd perspective made it hard to judge its true size, but I guessed you could have put a dozen semi trucks abreast and driven them from one end to the other with room to spare. Even so, there were no spars, ropes, wires, or girders supporting it—somehow the structure carried its own weight. Each island in the archipelago contained its own drive system, slaved to a central controller at Vox Core. Still, I couldn’t help wondering about the physical stress born by the link between these two enormous floating masses, even if the tunnel itself was bearing only a fraction of the load.

“Automated freight carriers pass through the tunnel carrying raw biomass to Vox Core and refined goods back to the farmers,” Treya said. “It’s not meant to be crossed on foot, but it’ll have to do.”

“How do we get inside?”

“We don’t. We might be able to do that from down in the farmholds, but not from here. We’ll have to cross on the outside.”

I held that thought for a moment, trying to keep it at a reassuring distance.

“There are stairs carved into the cliff,” she added. “You can’t see them from this angle. But they were cut during the original construction, so they’re probably somewhat eroded.” Even the foamed-granite composite the islands were made of couldn’t resist wind and salt water indefinitely. “It won’t be an easy climb.”

“The top of the tunnel is a curved surface, and it looks pretty slick.”

“It may be wider than you think.”

“Or it may not.”

“We don’t have a choice.”

But it was too late to begin the attempt, with only a couple of hours of daylight left.

*   *   *

We set up a fresh camp back in the forest. I watched Treya take another hit from her drug syringe. I said, “Is that thing bottomless?”