One of the shortest films produced by Studio Ghibli also happens to be one of its most perplexing: 2007's: Iblard Time. It doesn't have any real narrative across its half-hour-long runtime, instead opting to depict various strange landscapes that are occasionally inhabited by people, though never very many. This makes it feel overall more like an art piece than a film or a short film by any standard definition, but I guess it technically looked nice. It's got that going for it, at least.
I didn't really like how it sounded, though, and I wasn't able to get much out of it beyond admiring some of the images shown throughout. There are both better and worse ways to spend half-an-hour, I guess, and this could probably be recommended to those who just want to relax and look at some strange and kind of beautiful sights for 30-ish minutes, while being okay with probably not getting a whole lot else.