Underworld
UnderWorld
The setting for the fourth arc of the story. According to Kirito, it is graphically the most realistic of all VRMMOs to date. The flow of time in UW is much faster than the real world's (probably a prototype of the accelerated world). Even so, it seems that even Kirito was misled as to the actual rate of UW's time flow, so it is still unknown. However, in the "There is but one ultimate way" side story, the rate is said to be 10000 times faster than that of the real world.
Gun Gale Online
The setting for the third arc of the story. It is a virtual game world with a main focus on guns, although melee weapons like lightsabers and knives also exist.
Elfheim Map
Alfheim Online
The setting for the second arc of the story. It is a large world, divided into separate 'homelands' of each of its fairy races. All players have the ability to fly and have wings on their avatars. In the center is a very large tree called Yggdrasil, and the goal of the game is to reach the top. It implements a skill based system with players increasing their stats by developing both their combat and non-combat skills, in a fashion similar to the latest installments of the Elder Scrolls game series. Aincrad, the castle of the first game, is later accessible to ALO players as well.
Aincard
Sword Art Online
The first virtual game world, as well as the setting of the first arc of the story. The world takes the form of a giant floating castle called Aincrad, with 100 floors in it. Each floor has medieval-themed setting and a dungeon with a boss. The boss at the end of each floor has to be defeated before players can advance to the next higher floor. Like most RPGs, it implements a level based system.
