And indeed, that was the case. His grandmother was in charge of that mining project, which had seen several women take part, either in the management of the work or operating the drilling machines. At present, she only had the assistance of some younger women, all of whom were unmarried. Some were even still girls, but their mothers managed to take care of their offspring, either because they had other daughters helping them or because the girls themselves wanted to. That was the way of learning in that society: through practical experience.

When they arrived at the excavation site, Batro joined the other men to carry out their usual tasks: stacking materials, hauling boxes, piling debris, cleaning cleared areas… Meanwhile, his wife prepared to oversee the drilling work that the girls had to do with the pneumatic machines. One of them was Mondra, who was already there, staring at the crater they had drilled.

“I don’t get it, Lavidia. Yesterday, the pumps sucked up all the water, and as you know, the hole got filled up again in the afternoon.”

“Yeah, there must be some connection to a higher water table. You know, like the law of communicating vessels. We need to locate the communication conduit and seal it with concrete. Otherwise, we’re never gonna finish.”

“Yeah, sure,” she admitted. “The problem is that this morning... well, there’s no water anymore.”

“What do you mean, no water?”

“See for yourself.”

Lavidia and Mondra leaned over the crater, and indeed, that was the case. Where there should have been a small pond, the ground level had dropped, revealing a hole filled with darkness.

The two women carefully descended through the walkway they had set up a few days ago and peered to see what had happened. Water from the higher water table continued to pour through a side opening, disappearing into the hole, forming a small waterfall.

“I know what happened,” Lavidia concluded, after examining the fractured rocks. “The water was supported by a thin vault, and with more water, it gave way under the weight, fracturing.”

“A vault?”

“Exactly. Inside the earth, there was this empty ‘chamber’, perhaps a result of past magmatic activity. An air bubble formed that probably also filled with water, which has now seeped down to lower levels.”

Mondra looked at her interim boss with a somewhat puzzled expression. Lavidia continued:

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“Or maybe it was a hydrocarbon deposit, a reservoir, whose content followed the same path.”

“Okay, but why didn’t it give way earlier, with all the weight of the earth on top of it? I mean, before the excavation.”

“Oh, that’s easy. It was due to the ‘arch’ effect. The vault formed an arch, and arches in architecture are the most efficient way to support weight. The structure’s own weight

reinforced the arch, and by removing the earth that formed it, it lost its counterweights. As soon as the water came, the vault gave way.”

Mondra seemed to accept the explanation, and Lavidia shone a flashlight into the hole. But its depth and size were such that barely anything could be seen beyond the first few meters.

“And now, what do we do?” Mondra asked.”

“Well, this has saved us many days of work. The hole is already there. We just need to clear the surrounding earth, and we’ll reach the minerals we’re looking for.”

The excavators spent the entire day clearing the soil, and the next day they continued. As the area was cleared, they began to find increasingly strange things. Things that shouldn’t be there.

“Without a doubt, this is a wheel, Mondra. And what’s around it is probably the remains of a vehicle.”

“Indeed, that’s what it looks like.”

“How long has our settlement been inhabited?”

“I think my family and I were the first to arrive. I hadn’t been born yet, but my parents inaugurated this territory. At least on the west side of the river.”

They continued to advance and found increasingly fascinating things: fossilised remains of well-defined straight structures that couldn’t be natural formations, square structures with windows of the same design... All fossilised and half-sunken in mud that the passage of ages had turned into stone.

Finally, they reached another structure, another internal vault, which had also cracked. Perhaps due to the vibrations from the pneumatic hammer or the collapses from the previous night.

The vault formed a similar, even more extensive cavity, fortunately not as deep.

“Tomorrow we’ll explore this area, Mondra. How I wish my grandmother were here!”

“Yes, she knows everything. I’m sure she’ll give us an explanation that we can’t see right now.”

Lavidia could never have imagined, not even remotely, who would provide them with that explanation.