The Upside Down is one of the biggest mysteries in Stranger Things, and many fans have suggested the other dimension is the post-apocalyptic future.
Stranger Things season 4 has a lot of explaining to do after the events of season 3, but it also has to answer some mysteries left since season 1, such as everything related to the Upside Down. The other dimension is a mystery to viewers and characters within the series, to the point where fans have come up with many theories about it, and one of the most popular ones suggests the Upside Down is not a different dimension, but a look into a post-apocalyptic future. In 2016, Netflix released the sci-fi horror series Stranger Things, which went on to become a big success thanks to its tone, original story, combination of genres, and references to various works from the 1980s.
Stranger Things season 1 introduced viewers to the fictional town of Hawkins, Indiana, where a portal to another dimension was accidentally opened during a secret experiment taking place at Hawkins Laboratory. The first season focused on the disappearance of Will Byers (Noah Schnapp) and the discovery of the Upside Down, as well as some of the creatures living there. Stranger Things season 2 arrived in 2017, and followed the aftermath of Will’s return and the effects of his time in the Upside Down. Season 3 arrived after a long wait of two years, and revealed that the scientists at Hawkins Lab weren’t the only ones interested in the Upside Down and its creatures, as the Russians had established a lab underneath the new Starcourt Mall in Hawkins. In addition to that, the Mind Flayer was still around and had a bigger and more dangerous plan.