Yume Nikki has many interconnected locations that vary wildly in theme and size. They house the 24 effects also may also contain events.
The dream world is an intricate labyrinth of openly looping regions and obscure pathways, but most regions of the game can be considered as part of an individual 'world' with connections to other worlds. This is a list of all the central worlds of Yume Nikki.
Note: In this wiki, the commonly-accepted fan names are used so that they are easier to find, although each area has an official name that is also listed on their respective pages (which are the map names when viewing the game in RPG Maker, many of which are generic).
The Real World
The only location in the game that actually exists, though a dream version of it is present as well.
The place Madotsuki starts in, both in the real world and the dream world. In the real world she can play NASU and save the game, while the dream version leads to the Nexus.
The Original Locations
These are the places in the dream world that are accessible to the player from the very start of the dream, most of which having static, floating backgrounds and random objects plastered around. They lead to all of the deeper locations, and contain half of all of the effects.
These worlds are accessed from the original locations and have more depth and personality than them, as most of them do not contain simple looking backgrounds. The remaining half of the effects that the player must get are found within some of these places.
A rather large area full of trees that connects to various other locations. Rain falls heavily, and there are weird creatures that populate it. The Stoplight effect can be found here, as well as a few Jellyfish.
A vast expanse of curly plants and arid soil, reviled for being very difficult to navigate. Many events and the Towel effect hide inside. There is also a giant pyramid with a staircase that leads to the Sky Garden.
A moderately-sized world with many lamps. The smallest lamp takes Madotsuki to a sectioned off part of the Checkered Tile Path, and there is a hidden creature. The Lamp effect is found here. It used to be one of the original locations.
This FC World is a little less open-ended, with the overworld section being smaller. After crossing a tiny bridge, Madotsuki is taken to a small village with more Lizarmen and an entrance to the FC Dungeon.
This giant maze is very dark, requiring the Lamp effect. The walls are decorated with very odd looking faces that all look similar. The Famicom Glitch event and a way to the White Desert are found here.
A strange spaceship, complete with a piano and a nice view of space. It is owned by an alien known as Seccom Masada-sensei by fans. Upon sleeping in the bed, there is a chance that the ship will crash on Mars.