Castle in the Clouds is a 1st edition adventure from the "Old School Role Playing" company aka Joseph A. Mohr, who has produced a surprisingly large number of adventures (17 by my count) as well as a book of magic items, Malcon's Tome of Magic. I've got the latter but this is the first of his adventures I've bought. It goes for $3.50 and 25 or so pages, but it seems a bit pricey for what you get in terms of the adventure itself, it's more a mini-adventure with only about a dozen locations. The rest is mostly filler.
It's a case of where the title does describe the modules, it's set in a cloud giant's cloud castle. That has always been of of my favorite adventure ideas and it's largely been underutilized, I think. There was that goofy JG module with the balloon people, a couple decent Dungeon magazine adventures, but for something so much a part of folklore (Jack and the Beanstalk) and even music, it seems largely ignored. Compare it to Baba Yaga, who is much more obscure, yet her hut shows up all the time.
Apparently the PCs get to the cloud by special flying potions of handwavium. Once there they must fight or ignore the cloud giant guards in the tower and enter the dwelling itself. Inside are a cloud giant guard, a fomorian, some griffins, a cloud giant priest, a verbeeg, and then the cloud giant ruler and his pet magic-user. There's not much more to it than that, though their goal is to simply move the cloud castle (which is stuck because of an engine problem) and to solve that they need a gnome in the party. Never mind 1e gnomes tend to be illusionists, not tinkers (unless it's Dragonlance)
The creator has chosen to use art from Depositphotos.com. This ranges from badly drawn art to computer generated stuff to photographs. Usually it's reduced to tiny size. He uses a lot of it and the results are rather chaotic, almost like a Sex Pistols album cover. The map is made with campaign cartographer and so has an early 1990s look to it. Still, it's readable enough and he went with fit to height and single page as the PDF defaults.
Beyond that, there's really not that much to give the impression you (or the party) is in a cloud castle, other than the engine room, Stick with the adventure in Dungeon #16 (or the one from #9, though that's not nearly as good as the one in #16)