Surveying the Land?

[Tier-Group 3 Rooftop Observation Deck]

The World Tree had grown to about 1 m.

"Visibility was 400 km, was it?"

"By calculation, yes. Though if the world weren't a sphere, or were a sphere of a different size, the horizon distance would change too."

Looking down at the land beneath our feet from the roof of the Library-City Dungeon, one could see any number of plateaus and valleys spreading out. They were too far to see well even with a telescope, but in the distance lay several villages and towns. Far off on the western horizon mountains stretched out, and on the eastern horizon stood a single mountain as well. Within range of sight there was neither sea nor lake.

"The nearest town to the west is Iruma, then."

"To be precise, it's the castle this side of Iruma. Iruma proper is a village some three to four kilometers beyond the castle."

"That little town visible far to the east, that's Tsukuba's supply base? Other than to the west, it looks like roughly 200 km in every direction is uninhabited. If we subdued that town, things would become a good deal safer."

"At the present moment it's too far to conquer. Tsukuba is surely weakened for now, but in time some manner of response will be necessary."

"At this height you can't see the highway."

"Because it's a narrow, unpaved road."

"So the western mountains correspond to Chichibu. In Saitama that'd be 30 km or so, but this is probably about ten times the distance."

"The Kantō Plain is about 100 km on a side, but no mountains are visible to the north or south, and the plain in this vicinity appears to be about 700 km east to west and at least 800 km or more north to south. It seems to be roughly as broad as the North China Plain."

"And from here on, we turn this land into rich fields and paddies. Marie-san, about how far can you supply water?"

"If the canal gradient is one in a thousand, then from the foot of the hill the dungeon sits on, irrigation is possible out to about 10 km, at a 10 m drop in elevation. If we bury dungeon-structure water mains from the dungeon's foundation, then depending on the water pressure, sending water out 100 km or so should be possible."

The dungeon itself sits atop the hill, but underground, naturally, there is a dungeon-structure foundation that supplies energy from the Core.

"A radius of 100 km, then."

"Excluding the western side, since Iruma is there, a radius on the order of 100 km gives 20,000 km², of which the arable land would be, in theory, about 1,000,000 chōbu. In other words, a Million-Chōbu Reclamation Plan."

"It has a nice ring to it."

"It isn't my original. It's a policy from the Nara period of the otherworld. Since there were no dungeons, it failed, of course."

"And if a dungeon means it would succeed, that means, what, making the fields and paddies out of dungeon structure, like building walls?"

"Both paddies and canals are comparatively simple in their basic shapes, so we make those out of dungeon structure. Of course their upkeep requires dungeon energy too, small amounts though it may be, so we proceed in order, in step with the rising population."

"So come autumn, even if it's only one corner at the foot of the tower, we'll get to see golden ears of rice."

"That will be so. No, we will make it so."

What they were doing was kunimi, a surveying of the land from on high, but to say so outright would be an act of lèse-majesté. Though, mind you, the gods of Japanese mythology are, beginning with the chief deity, rather a pack of useless good-for-nothing goddesses: lured out by a naked dance in the myths, or appearing in Emperor Yūryaku's dream to complain about having to eat their meals all alone.