Doryani's Machinarium Maze Map is a rather new map in Path of Exile that works a lot differently from regular Unique maps. During the map you get to make decisions that affect the final boss of the map, and the rewards for completing it. It's a fun map, but obtaining it is more difficult than regular Unique maps that can drop from pretty much any mob.
The Doryani's Machinarium map can only drop from a boss called Ahuatotli, the Blind. This is a boss that will only spawn in Vaal outposts inside The Azurite Mine, and has a random chance to spawn in any eligible area. So to get it you will need to farm a lot of sulphite and go delve into the mines until you get lucky with a Vaal outpost area.
Ahuatotli, the Blind can also drop other Unique items, so the map is not a 100 % drop.
If you don't want to delve, but still want the map, then it's of course possible to buy it from another player. The map is kind of expensive though.