A «Mirage Sphere» (ミラージュ・スフィア, Mirāju Sufia?) is a device in «Sword Art Online» that can produce a map of a chosen area in 3D.
Description[]
The Mirage Sphere is a sphere-shape[1] yellow[2] device with an intricate design on its sides[2] and a shining crystal ball inside[1].

A Mirage Sphere in use
The Mirage Sphere is activated by clicking on a button at the top of the sphere and selecting the desired location via a pop-up menu.[1] When activated, the sphere splits into two, with the top half rising and leaving behind a column of light.[2] Once the top part of the sphere stops rising, five panels open up from the sides of the top of the sphere and the column of light is then changed into a sphere, forming a holographic map.[2]
Although a simple 2D map can be called out from the player's menu, the Mirage Sphere portrays the map features, like trees, in 3D and great detail.