It was a little over a day later that they reached the foot of the mountain, climbing out of the tube station and up to the surface. “Welcome to Everest” Oldra read as they walked out into the foothills around the colossal peak. “Can’t believe I’ve never been to the tallest mountain in Earth before.” She said, glancing up at the huge mass to the north of them. 

Ithaca followed her gaze. The mountain was so vast that rain fell frozen onto it’s peak, and blew off in high winds in a stream of glistening powder. It was doing that now, a cloud of frozen water spilling from the highest peaks and drifting towards the west where the cold air of night still drew wind towards.

“We sure we’ve got everything?” She asked, as she shuffled the pack on her back. “I don’t want to have to turn around straight away and go back.”

Dannal looked through the pack on Ipra’s back, and nodded. “We’ve got everything. So, where do we go from here?” He asked. Ithaca opened her palm, and the hologram of the mountain filled her hand. She peered closely at it, and frowned.

“Back, the way we just came.” She said, turning back into the station terminal. The others followed her into the shade as she consulted the hologram. “Looks like we need to continue into the mountain from the station.”

“But there is no way into the mountain via the tube system.” Said Ipra. “The tube curves around the entire range from here, then meets up with the lines towards Ortanath once around to the north.”

Oldra looked around at the station. “Well, this place is wider than I would expect for a station this small. Maybe there used to be a line into the mountain?”

It took them an hour to find someone who worked in the station to ask, an older human who was supervising the cleaning droids as they worked to remove some mould from a poster frame.

“Into the mountain?” He said softly after they explained what they were looking for. “I think it did, but that was a long time before I was born. Yes, I recall now, there used to be a line straight through the mountain.” He said, nodding hard, his thin white hair bobbing with each nod. “But given it’s only a few extra minutes for people to go around rather than through, they just decided to rebuild it safer.”

Ithaca turned her back and consulted the map again, before turning back to face the old man. “So, is there any way we can get into these old tunnels and have a look?” She asked.

The old man scratched his chin. “Well, it’s closed to the public…” he started, but Dannal interrupted.

“We’re actually going spelunking. If we can see where the tube used to go, we can map it as a possible emergency route back to the surface if there’s an accident. Taking these things into account could save lives in the long run.” He shrugged. “Plus, we can map it for damage that could threaten the station, for free, and possibly save you and the station master money down the line if you need to make repairs.”

The old man sighed, and waved vaughly at the robots. “Come on, I’ll show you where the old entrance annex is.” He said. 

They followed him back towards the tube terminus, then to a blank wall. “The tube used to continue through here, it got sealed up ages back.” The old man said, then lead the way to a small door recessed into the wall. He unlocked it. “Beyond this point, the main lights aren’t working, just the emergency lamps. You kids need torches or…” he trailed off as Oldra and Ipra both pulled lanterns from their packs. “You kids are prepared, arn’t you?” He chuckled. 

The door creaked open, and the waft of stale air passed over them. “If you kids run in to any problems, there are emergency ports every few hundred meters. You’ll be able to call for me or anyone else in the station from there. Same goes for if you find anything that could cause trouble to the station.” He added.

They thanked him, and passed through the door into the gloom beyond. Small lanterns lined the walls, set into small alcoves that reflected light out into wide patches of light, and deep patches of gloom between them.

“It’s weird not being able to see any daylight.” Said Dannal, peering into the grey murk deeper down the tunnel. “I wonder if anyone lives down here.”

Ithaca opened her palm and the glow of the hologram barely added anything to the dull light around them. “Looks like we go this way.” She said, ignoring the vaguely worrying ideas that Dannal had put into her head. She took the lead, pulling a torch out to add to the dull lantern light. 

They passed aging signs and adverts pasted to the walls for products that were tens of thousands, sometimes even millions, of days old. Some of the products were still sold, some were long gone, replaced with new stuff, or just fallen out of fashion. Soon these faded away, and they reached the end of the platform, climbing down into the shallow bowl of the track tube. 

The lanterns became fewer as they pushed deeper from the station, set now only into the tube’s reinforcing rings at regular intervals, forcing the four to pass through extended periods of gloom. Occasionally, Ithaca would consult the hologram, but they kept going regardless, deeper and deeper under the mountain.

After a few hours, Oldra, who was at the back of the party, stopped. “Can you hear anything?” She asked, peering back the way they’d come. Feeling a sense of dread, Ithaca turned off her torch and came to join her friend.

“What did you hear?” She asked softly, as if not wanting to tip off whatever could be behind them. 

“I don’t know-“ she pointed suddenly. “There, I saw the light change.” Ithaca followed her finger, and sure enough, the grey gloom a few miles back on the straight tube changed, growing brighter for a moment.

“Someone is in the tunnel behind us.” Said Ipra, squinting. “I cannot be sure, but I would hazard a guess at a half dozen at least with torches.”

“Our old friend Notrotu?” Asked Oldra, and Ithaca shrugged. 

“I don’t know, and I don’t care. Let’s get moving.” She said, turning her back on whoever was following and turning on her torch again.

They moved as fast as they could, with Ithaca’s hand open constantly so she could study the map as they went. If there was a way out ahead, she didn’t want to miss it and have to double back for it. If she hadn’t been doing that, they would have missed the route the map wanted them to take when they passed through a section of tube that seemed no different until Ithaca stopped. “Wait, we need to go left here.”

“Left through what?” Asked Dannal, glancing around the section of tube. “It’s as flat and featureless as the rest, where do we go?”

Ipra was touching the walls at the last tube join. “This is a switching section.” She said suddenly. “If we can get something in to this gap, we can open it.”

Oldra went through her pack, and produced a climbing axe. They slotted it into a gap, and with all four pushing together, managed to break the gap open. The smell of age thousands of times stronger than what they were breathing washed over them, and Ipra stepped through, bracing as best she could. “The pistons are trying to push the access closed again. Please hurry.”

The three humans ducked under her arms, and she walked back to a point where letting go wouldn’t crush her. She slipped her arms out as the metal pushed closed again. They braced for a clang, or a shock of the impact, but it was silent and smooth as if it was brand new.

“So, that should buy us a few hours.” Said Dannal. “We didn’t see this turn, so they might not either.” He looked around to find the others were already moving away up the tunnel, and he jogged to follow.

The tube took a few turns, left then right, and into a vast station, hundreds of times bigger than the one in the middle of Great York, with a rack of tube cars stacked to the side of the main platforms to feed them with passenger conveyance.

“What in Earth is all this for?” Asked Oldra, looking over the time faded stone floors, the markings not worn by anything other than extreme age. “I don’t think anyone’s been in here for billions of days.”

Ithaca walked down the side of station, looking at the posters. The lettering was human, she recognised the letters, but not the words. “It’s like it’s fallen out of time.” she said, running a hand over a sign with a large arrow pointing towards one of the boarding points for a tube car. “Like something you’d see in a history book.”

“The technology’s way too good.” Said Dannal, looking over a light fitting. “This stuff is better than what we use now. Whoever built this place,” he leaned back away from it, “they built it to last.”

Ithaca consulted the hologram. “Okay, we should go through here and…” She paused, looking at the room she’d just reached. “It’s a dead end.”

The others joined her, looking around the sizable room beyond the doorway she’d stopped in. Ipra leaned in and studied the walls nearest the door. “It is a lift.” she said suddenly, sounding as surprised as anyone of her race could.

The others shone their torches around, and Ithaca slipped inside, looking at the floor indicator. “This thing only goes down.” She said, studying the markings above the door. “At least, assuming it works left to right like a normal lift. It’s currently set to the top floor.”

The others joined her, following her gaze. “So, this was for a mine of some kind?” Suggested Oldra, trying to find numbers on the readout but unable to see anything familiar in the odd shapes of the charcters on the floor selector.

“That connects to a public tube line?” Asked Dannal. “No, this is something, much weirder.” He walked over to the floor selector. “I wonder if it works.” He muttered to himself, and pressed the lowest floor selector.

The lights sprang into life, a soft, warm light filling the small room. “What did you just do?” Asked Ithaca, walking over to Dannal, who was looking past her, to the doors.

They had, without making a sound, slid closed.

“I just, you know, it’s ancient so I didn’t think there was any power!” He said, raising his hands defensively as she walked towards him once more.

“What was that?” Said Ipra suddenly, and everyone paused. There was a clunk, then another one a few seconds later, then a voice spoke. It was a human throat, but the language was beyond Ithaca. Then, the room started to move, first with a soft judder, then sliding down a few inches.

Then it dropped like a stone.