Well. He is not super happy about this but so long as he can see his balloons if he looks back when he's about a third, a half of the way there, he will continue onwards.

He's going to fly up the steps unless there is some other issue with that.

Doesn't seem to but then his vision gets—

—weird—

—and it's not a temple anymore, the stairs lead to a platform, beyond which there is a city.

He stops.

Is there still a set of steps to walk back down, should he so choose? Because he will if so. Just to check it's two-way.

There is!

...it seems to break off into the untold depths, from where he's standing.

Okay, well, he will land and walk back down. He can drop into the untold depths if in fact present and not just an illusion and then he can fly back up.

—weird vision—

—steps down from the temple.

Okay, well, back up and to the city it is.

He doesn't like the weird vision effect. It's annoying.

The city also extends as far as the eye can see. There are lights, but no people. Looking at it is also weird, and feels like looking into a mirage, or the water, or hot air, with occasional ripples the eye can't really see when he focuses.

He sorta likes the color scheme? But he's a bit confused by the lack of people.

Can he go up to one of the buildings and poke it? He dislikes the mirage feeling.

Yeah it's all pretty solid.

And pretty tall. From the ground up, the tallest buildings are skyscraper-height.

… If he flies up a bit and pokes somewhere higher up, also solid?

Yup. All very solid.

The inside of the buildings, though... is a bit less defined.

… He hopes nobody minds if he turns the glass of a window to air.

Assuming he can. Assuming it's non-magical.

It's very magical.

Any doors?

Locked. Magical.

… Can he use a sharp blade, again, perchance?

Sure!

The other side of the door looks like what someone dreaming the inside of a building might be.

… Are things still pokeably solid?

Kiiiinda. They're solid but they're not necessarily where it looks like they are. It's all very optical illusion-y.

Okay. He's gonna back away from the building, then, and keep note of where he started – is it obvious and noticeable or should he build something to mark it?

It is pretty noticeable!

He is going to put a small red cube next to it anyway! Just so he knows that it's the right noticeable exit!

Then he'll continue onwards. Any people?

Nnnope.

Any interesting buildings that look slightly less dream-like or whatever on close inspection? Or perhaps interesting buildings that do look dream-like but that might be interesting on the outside anyway?

Anything written?