Testmap
Testmap is an unused area left in Pikmin. Judging from the name, it was most likely used for testing purposes.
Video footage
A video showing the map: {{#ev:youtube|7sEvgTUbrtI}}
Geography
The area consists of a very complicated design with many pathways and arches. The S.S. Dolphin is on a flat, arch-like structure that is raised high above the ground while the Onions are above a lowered maze-like path. The paths that the Pikmin return objects to their Onions to are obviously not complete, the Pikmin usually just run into a wall. The area's textures are mostly for testing and typically aren't very special in particular. There are many polygons with holes in them that Olimar can fall through and walk around on, most likely for testing purposes. There are also step-like platforms probably used for measuring the height of some objects in the game, and even a pathway with many deep holes that the Captain and/or his Pikmin can get trapped in. The map is probably the largest in size compared to even play_4. The map doesn't have any boundaries, either, so if Olimar were to accidently walk off, the only cure is to reset the game. There are also many bright red pathes that lead above the ground and in many directions, very similiar to the arch that carries the Dolphin, but the latter is much larger. The design is rather confusing, seemingly just all over the place. It's more than likely designed just for testing, as programmers didn't expect players to be able to play such an area.