A jagged gash opens in the air, silent and sinuous, first slashing a rough curve through reality and then spreading open farther as though grasped and pulled by some vast alien force. It twists through space, shuddering and pulsing like a creature in pain, wider and wider until—at last—a person tumbles through and it snaps shut all at once with a thunderous crack.
"Thanks ever so!" She puts on her armor and does a happy little twirl and then dashes off across the flattened tundra.
He watches her for a minute and then turns and heads back to civilization.
And for a week, nobody bothers her. What does she do with her week?
Well the first thing she does is get to the far edge of her flattened tundra and then start digging an enormous pit. She's found the ceiling of the world; she intends to locate the floor, if there is one, and then count up the heights and see if sea level is consistently midway between.
There is, indeed, a floor. It's not perfectly even; it's somewhere between 58 and 62 blocks below sea level. She can build up by 193 blocks from sea level, so, not even close to halfway.
That's a weird enough set of numbers that, especially with the variation, she is suddenly having Doubts about things she previously took for granted. Like, is sea level the same everywhere, really truly? Is the ceiling height the same everywhere, really truly?
Is she going to mark two places where she believes there are separate bodies of water she's been referencing sea levels off of at various times and then build a horizontal bridge between them to check whether they're the same height? Is she going to then repeat this experiment for a separate set of distinct sea levels? And additionally build heavenstairs in all those places to check that the ceiling is the same distance away? Yes. Yes she is absolutely going to do all those things.
The sea level is the same everywhere! So is the ceiling! The numbers between sea level and the uneven floor are the same, as well.
Okay. Her curiosity about heights is satisfied. For now.
...there was a whole lot of stuff in those pits that she ignored at the time because it stood between her and her goal. She goes back and looks at the chestsful of random objects scattered by the rims of her Floor Holes. And conscientiously puts up CAUTION signs all around them, in case anyone wanders close enough to risk falling in.
Random objects: Cobblestone, mostly. Loooooots of cobblestone. Kind of ridiculous amounts of cobblestone. Quite a bit of dirt and coal. Some iron ore. Some... redstone dust, whatever that is? There's a cave with lava that she passed through in one of the holes; if she looks around in it she'll see something blueish-white and reflective on one of the walls as well as a dark black glass-looking thing on the floor next to the lava.
She does, in fact, investigate the cave, once she remembers its existence. The shiny objects are intriguing. Reveal your secrets, shiny objects!
Shiny object on the wall is diamonds! Shiny black floor is obsidian; some of it she can mine safely but some of it ends up being lava once mined.
Peculiar. Definitely worth a chapter in her forthcoming book on the wonders of Cubeland. She sets a slightly absurd quantity of cobblestone to cooking in a slightly absurd edifice of stacked furnaces, because it's just so much more aesthetically pleasing in its original form, and further investigates the mystery of obsidian. What is it doing when it ends up being lava, and why does it do that? There's some relationship between obsidian and lava in her former world, she's vaguely aware, but she bets their relationship here is very different.
Looks like sometimes there is lava behind the obsidian, and breaking the obsidian lets it flow out.
If she experiments some more, she’ll find out that if still lava touches still water, or if flowing water touches still lava, it becomes obsidian. If flowing lava touches still water, it becomes stone. If flowing lava and still water meet, they form cobblestone.