Tunnels 02, Deeper by Roderick Gordon, Brian Williams

I've seen these before, in the foundries in the South Cavern of the Colony." Cal lifted his chin and regarded Chester truculently, as if he had proved his superiority over the older boy. "The Coprolites must've been smelting pig iron here."
    "An age ago, by the looks of it," Will said, gazing around the place.
    Cal nodded, and, there being nothing else worthy of note, they trooped along the tunnel in silence.
    "He's a smart aleck," Chester said when Cal was far enough ahead to be out of earshot.
    "Look, Chester," Will replied in a low voice, "he's probably scared stiff by this place, like all the Colonists are. And don't forget, he's a lot younger than either of us. He's just a kid."
    "That's no excuse."
    "No, it's not, but you have to make a bit of an allowance," Will suggested.
    "That's no good down here, Will, and you know it!" Chester blurted. Noticing that Cal had heard his outburst and turned to look at them curiously. Chester immediately dropped his voice. "There's no room for anyone to mess up. What, do you think we can ask the Styx for a second chance, like having another life in some stupid video game? Get real, will you?"
    "He won't let us down," Will said.
    "Are you willing to bet your life -- your one life -- on that?" Chester asked him.
    Will just shook his head as they continued to plod along. He knew that there was nothing he could say to change his friend's opinion, and maybe Chester was right.
    Away from the furnaces and the mounds of silt, they found the floor of the tunnel compacted, as if many feet had trodden it into a firm surface. Although they kept to the main tunnel, every so often smaller passages spun off from it. Some of these were high enough to stand in, but the majority were mere crawlways. The boys had no intention of leaving the main thoroughfare, and they eventually came to a place where the tunnel split.
    "So, which way now?" Chester asked as he and Will neared Cal, who had come to a stop. The boy had spotted something lying at the base of the wall and went over to it, nudging it with his toe cap. It was a signpost of bleached, splintery wood with two "hands" affixed to the top of a broken-off stake, their fingerlike extensions pointing in opposite directions. Cal picked up the stake and held it so Will could read the barely legible writing carved into each.
    "This says CreviceTown , which must be the tunnel to the right. This..." he faltered, "I can't quite make it out... the end's been chewed off... I think it says The Great something or other?"
    "The Great Plain," Cal volunteered immediately.
    Will and Chester regarded him with not a little surprise.
    "Heard my Uncle Tam's friends talk about it once," he explained.
    "Well, what else did you hear? And what's this town like? Is it a Coprolite place?" Will asked him.
    "I don't know."
    "Come on, should we go there?" Will pressed him.
    "I really don't know anything more," Call replied indifferently, letting the sign slide to the ground.
    "Well, I like the sound of the town. Bet my dad would have gone there. What do you think, Chester, do we go that way?"
    "Whatever," Chester answered, still staring distrustfully at Cal.
    But as they ambled along, it became evident in only a few hours that the route they'd chosen wasn't a main thoroughfare like the tunnel they'd left behind. The floor was rougher and loosely packed, with large chunks of stone strewn across it, suggesting that it wasn't used very often. And, even worse, they were forced to climb over large falls of rock where the roof or walls had partially collapsed.
    Just as they began to deliberate whether to turn back, they rounded a corner and their lights cut a swath through the darkness to reveal a structure barring their path. It was regular and clearly man-made.
    "So there is something here after all," Will said with a gush of relief.
    As they neared the obstruction, the tunnel ballooned into a larger cavity. Their lights revealed a tall, fencelike structure with two towers, each about