"What does your moon house look like?"

"Want to see it?"

"Sure, but you'll have to provide air."

"I promise I was not going to forget air."

Portal!

She steps through.

And on the other side is a broad courtyard, gravel paths winding between slender trees and marble fountains. He hasn't done anything to the gravity, but he's obviously done something to the atmosphere, because there is one.

The dominant colour is pale grey; even the trees and flowers are nearly colourless, just a hint of green lingering in the leaves, a touch of pink in the petals. The restricted palette lends the place an ethereal air, especially in combination with the architectural style, which favours spare lines, delicate curves, and organic asymmetry, and takes advantage of the low gravity to climb in otherwise-hazardous proportions up to otherwise-impossible heights.

"Oh goodness. It has almost the quality of a foggy day without the actual fog, with the grey. - Does low gravity make flying very different?"

"Yeah, it's kind of interesting. I'm not sure if it's more fun, but it's interesting. And as you can see, you don't need to worry about the air."

"I noticed that!" She tries jumping and flares out her wings at the peak.

Low gravity: so floaty! The Emperor leaps up after her.

And she will flap around peering at all the architecture and complimenting the best parts.

There is a lot of architecture. He said 'building a house', but this looks more like a palace, or maybe a small town.

"This is a lot of house."

"I had a lot of room to build it in!"

"So you did! Is anybody likely to live in it?"

"Oh, eventually I'm sure I'll make permanent portals and people can come up here whenever they like, but I'm not in a rush."

"And the atmosphere doesn't need maintenance?"

"Nope! I did the magic and it's done."

"Cool. How far does it go?"

"Not as high as the air on the planet, but everywhere."

"All over the surface of the moon, you mean? Wow, that didn't take you long at all."

"I wouldn't know how long this sort of thing is normally supposed to take!"

"The Valar are pretty temperamentally slow on anything that isn't desperately urgent, and their sense of urgency needed some calibrating. They could give a moon air, but it would take years, probably."

"If it took years I'd get bored long before it was finished!"

"Then it's good you're so fast."