Over the years, fans have raised a number of serious challenges for understanding how to make sense of what has been established about the Matoran Universe's geography, and I've mentioned in passing several theories about them. This topic is an attempt at a definitive explanation, and map, of the geography of the domes and how they fit inside the giant robot.
Partly to help me figure it out in the first place, and partly because a picture's worth a thousand words, here's a map (version showing Barraki territories). I recommend viewing fullscreen to read the font better, or zooming in and scrolling around. (Click the thumbnail.)
Non-Barraki version (designed to avoid overlapping parts so it's easy to edit)
This is the version of the Matoran Universe that I am using for a canon-fit retelling of all of Bionicle history I'm writing. I'm trying to make everything about this story feel as definitive and complete as possible while being a fun read, and later I plan to post a complete protodermis theory (draft already written) as well to go along with it. Not sure yet if I'll do any other theory topics for it at this point.
So, here's the canon facts in question.
First, the source files.
This is a concept art version of the giant robot, which I used (just the robot itself) to get an outline that represents a cutaway view which I could draw domes on. (All editing done in GIMP.) It might not be fully canon, but seems more or less the same as the canon portrayals (see here for various related images). Note that the ball pose and both versions of the prototype robot shown in the original image are clearly non-canon.
And this is the famous map of the Matoran Universe that doesn't show domes or tunnels, and clearly has some canon errors.
For example, Voya Nui could not possibly be anywhere near as huge as depicted there, since it ripped a hole in the top of the giant robot during the Great Cataclysm and let water pour down in; if it was that big, the whole thing would flood within a few hours to days, but in actual canon, it has only made a small lake after 1000 years. More mundane issues show up with the placement of each land in relation to its neighbors -- it's impossible to just overlay this map on the giant robot's outline and have all the land fit inside. Some have to be sized down, and nearly all have to be moved.
Another major issue that I ran into immediately was that even though the Southern Continent is canonically the biggest, all depictions of the robot's lower torso show barely any connected space, while the chest is huge. Were I making a map based on the robot's design, I wouldn't even have a continent there, and I'd have a huge one in the north.
I solved this by first sizing down everything significantly, and vastly increasing the distance between every land.
I had to move Daxia a lot specifically to get the SC to be as large as possible. And since there are some obvious spherical parts to the robot's design, including a large one in the lower middle of the chest, I aligned several domes with these, and put the NC in that large chest sphere. I also put the other torso islands in their own domes, and moved them significantly so they would be more geometrically aligned.
An alternate explanation of the chest region could be that it's all a large rectangular chamber with rounded edges, rather than a true dome, and the arrangement of the NC and the other torso islands like Zakaz and Stelt could be left as-is from the original map. This is almost as plausible as my more complicated interpretation, but it would make the ceiling be seriously unsound structurally, without invoking massive pillar supports. And the description to the right on the canon map clearly states that there are domes of varying sizes and that the continents are in domes, so the alternate explanation would require us to redefine "dome".
Another possibility is that I'm right to put each major land in a separate circular dome but that they actually are arranged in a random jumble inside the robot's chest. But that doesn't seem very robot-like to me.
It's canon that there are tunnels that connect different domes, and where these pass through a bending or swiveling joint in the robot, the tunnels bend.
The artificial gravity bends along a floor of these tunnels as well, and they are all filled with water -- except that it's confirmed the tunnel between Karzahni and Metru Nui is just land, with a peninsula jutting into Metru Nui. I assume that is meant as confirmation that the tunnel between those two lands is not flexible, which would imply that Karzahni needs moved way up away from Xia, into the back of the mouth area of the head (below the brain). There would be some other non-bending tubes as well, between the domes in the upper torso for example, or between domes in the same solid section of a limb.
I assume the tunnels are designed with many mobile ring sections circling the tunnel, so the whole collection will bend much like a LEGO Technic flexible tube.
A major mystery that has confused many fans is the sea gates leading from Metru Nui to other lands, apparently conflicting with the fact that Karzahni looks like it's in the neck and yet is a forgotten and forbidden land. So I have proposed that there are two extra tunnels leading from Metru Nui through the tubes on the sides of the neck to the torso. In total, there are thus three routes from MN, but the middle one has land obstructing it, so it is not a sea route. So the oft-mentioned "sea gates" are two in number, under this theory.
Although we should keep in mind that a single route around Karzahni and through the neck is also possible, as "gates" in the plural can still work as long as the tunnel has a gate on the left and a gate on the right, rather than one gate with a hinge only on one side. It's also possible both interpretations are true at the same time, so you could say there's "four gates".
For a reply in a previous topic I looked up the only depiction of this in Time Trap, when TSO & Sentrakh go through a sea gate, and it doesn't say. But it does say that it was "torn open". If it had hinges at all I wouldn't expect that description. I suspect it is lowered on a pulley and weight system. Note that the Mangai's gate on a land route was lowered into place, so there's nearby precedent for that interpretation, plus it would be more secure. All that's confirmed, though, is that it's metal.
I invoked a whole dome for the uninhabited (other than Rahi) island that Xia destroyed since it was blocking a major trade route. This happened to match the geometric pattern I had in mind, plus it forms a line to Odina, the Dark Hunters HQ, which seems to me to be the most likely place this particular route would head to. The BoM HQ moves around, and Toa are all over, etc.
I moved Zakaz quite a bit, partly because Ehlek's territory included both it and the western island chain. On the original map this looks a bit surprising and random, as Zakaz is in the middle, not to the west. This way it makes more sense.
I also moved Stelt a good distance, much more to the north, so it is central to the torso regions. This is another big stretch, but it seemed natural once I moved the NC to that sphere. An alternative explanation could be that Stelt is in a dome to the east of the NC (I included none there), and there'd be a matching dome to the west, getting a question mark as with two other domes to the south. But my way, Stelt is more central and this seemed to fit its highly varied nature better IMO.
I would even go so far as to propose Stelt as the island the six Barraki would meet on from time to time, including when they demanded the Brotherhood make Rahi for their military use, and when Teridax ambushed them. Admittedly there are other good candidates for this, though, especially Xia. Zakaz or a part of the NC would work too.
Another point of confusion in the official facts is that Artakha is portrayed as a huge, hard-to-miss island in one of the shoulders, and it's known that the islands you have to go through its dome to get to are part of the inhabited, interacting culture that excludes the Southern Chain islands -- they presumably get a lot of travel. To solve this I came up with a few ideas.
First, on the official map Artakha is shown a lot more to the west than others so I think instead of being centered in its dome it's off to one side. There could be constant fog, similar to the fog we've seen around Metru Nui, and since the tunnels are at an angle, if you sailed as the crow flies between them you wouldn't reach the center of the dome anyways, much less the northwestern side.
Second, the concept art of the giant robot shows a tube with seemingly no purpose connecting the lower part of the chest to the armpit, basically (the upper inner side of the arm itself, that is). I propose that this is an alternate, backup route between the other islands in the arm and the torso besides the tunnel between Artakha's dome and the torso. Bad rumors about its dome could have been spread (landless but dangerous, perhaps due to First Rahi or the like) so that people would intentionally avoid it, while having no idea they are avoiding a landmass.
This setup is mirrored on the eastern side but there would be no such fear about that shoulder dome.
Another big reason I made this map was to visually try to theorize where the approximate borders of the Barraki's territories were, in the League of Six Kingdoms. We know a lot about this, but most of the descriptions are vague, other than confirmation that Ehlek had Zakaz and Pridak had Xia. We also know some islands that are out of their control, as BS01 says:
It doesn't mention Destral, but I've shown Destral as floating in its original location and outside their territory. I don't know (and have failed to find an answer so far) whether Destral was already teleporting around during the League, but we know that the Brotherhood met with the League and was forced to make Rahi for them. This implies they were under League control, politically, but may also imply that their land was still ruled by the Makuta, not the League, since they had to meet "in a Barraki tower" (according to BS01's timeline), rather than simply in the meeting room already built on Destral (where the Convocation later took place).
My Artakha theory explains its exemption, and the active ban on going to Karzahni in early years explains that. Metru Nui is confirmed to have gotten a special deal. The Southern islands simply remained unexplored (it seems it was a nearly universal trait to not want to travel that far among the northern population).
What about Daxia? If it has its own dome as I depicted (which may very well be wrong), you'd think they'd look for an island in that dome, and I doubt we can invoke the "scary waters" explanation twice. However, the fortress is apparently hidden inland, and the climate is oppressively hot, plus the land is confirmed to have a few dangerous Rahi species. So they may have just assumed it was uninhabited, and didn't want it themselves either.
Another problem in figuring out Barraki territory is that a full three of them are mentioned as having western lands, but only Pridak is ever mentioned as having eastern lands. He's said to have "northestern" lands, including Xia.
But what about the more southernly of the islands in the left arm? I assume that another Barraki would not have these because they'd have to travel through the northeast (Pridak's area) to get to them. You can't just travel as the crow flies between the SC and Visorak or Nynrah. Also, Nynrah is closely related culturally to Xia even though they're so distant. So the simple solution is to define "north" in comparison with the extreme south, and give Pridak the whole left/east arm plus Xia.
I also gave him Stelt, with the idea that it's where all the Barraki would meet from time to time, so is sort of the HQ of the League, but this theory could be completely wrong. I chose it mainly because it's such a varied island which seems to imply something like neutrality, and in more modern times they try to tear down any building. They could have gotten the idea from the Brotherhood tearing down the Barraki main fortress if it was there. Of course, the Skakdi do the same basic thing. On my map Stelt is central to the northern regions, but on the original Zakaz is.
However, Pridak is sort of the leader of the Barraki, and Zakaz is confirmed to be Ehlek's territory. I would think their central ruling place would be in Pridak's land. So that narrows it down to Xia (confirmed in his land) and Stelt (not confirmed). In my theory, Xia is Pridak's personal HQ, as he seems to really like the place, which could make it less desirable to the others as a place for them all to meet. The others would have their own personal HQs too, like Ehlek's on Zakaz.
Kalmah is "northwestern lands" (yet this has to exclude the actual northwestern lands on the official map, Artakha and Zakaz). I presume this means the northwestern part of the NC, or perhaps the whole NC. I gave the main mass of that continent to him with no other land, but excluding the Tren Krom Peninsula.
Takadox is "southwestern lands". Yet, Carapar is not contrasted with southeastern, which would have made it easy -- Carapar is given "southern lands".
I interpreted this as saying Carapar gets the southeastern tip of the SC (which reaches farther south than the southwest), plus going up a bit on the east side, and then the northernmost of the Southern Chain islands (Artidax, etc.). So Takadox gets the whole western coast of the SC and much of the land in between (mostly unpopulated).
Mantax is given "central lands". That could mean a lot of things. I think he's the other main candidate for Stelt, since it's central-east (in torso) on the original map, but I've already explained above why I doubt this. I suspect Mantax originated in the northern coast of the Southern Continent, which is probably where most of the villages, towns, or cities are. So I think his main territory is the northern, most populated, part of the SC. Plus I have him given the Tren Krom Peninsula as a bonus to make his total region seem more "central".
Note that there is an artificial gravity field throughout all these domes, defining the robot's back (and, when the limbs, neck, or waist bend, the back of that particular part) as "down". Yet when the robot stands up on a megaplanet, on dry land, as Mata Nui was constructed standing in the Great Barren and Makuta later stood on Bara Magna, there's a hatch at the bottom of the foot and people come out with "down" being true down.
So I propose that the tunnel between the southernmost domes and these hatches gradually twist, including the grav field, to align with true down. The effect would be almost imperceptible as you went along it.
An open question I have is whether this tunnel has water in it (which could risk a leak thanks to the altered gravity), or whether it's a land route. On the map as I have it you could interpret it as water, but in my story I've defined it as a land route. I just didn't want to show land since it's not confirmed. What we do know is that some stretch of it at least is land, between the main tunnel and the hatch itself.
In my story I invoke a sea vessel designed by the Great Beings and used by them for travel, to be docked wherever the water ends and reached on foot after entering the hatch. Something like this would make sense to explain how they traveled around to do the various chores just before the robot launched, like moving Tren Krom or hiding the Ignika.
Another issue I made no attempt to theorize for is that we know of more minor locations including "islands" than there are islands on the map that aren't already known.
It can seem like this wasn't thought through very well, but this is easily solved with two explanations. First, some of these locations are almost certainly the same. Like, the unknown island where a particular minor battle took place could also be the island where Lesovikk's village was with the insane Turaga.
Second, there are some confirmed tiny islands (I would call them islets) within the same dome as major islands, generally too small to show up on either the official map or mine. This could also work if they're large enough to show up but Greg simply didn't bother to include them on his map. Metru Nui has one confirmed. Artakha's dome used to have a second island but it was later destroyed. The Dark Hunter Tyrant's homeland is said to be a small island south of Odina -- this may be the one in its own dome shown on the map or a tiny island in Odina's dome.
Also, in at least one clear case, in the right leg, there are two islands (I nickname them the Endquote Islands for their shape ) that are side by side, so apparently have to share a dome. And a few domes north of there, two other islands seemed too side-by-side again to not share a dome. Artidax actually could be interpreted as a third island sharing that dome, but I felt this made no sense because it's been explored and they haven't.
Incidentally, here's a bonus theory to help explain why those Southern Chain islands remain so unexplored.
Since Artidax was placed so close to the islands south of it, I propose that it's almost flush with the tunnel connecting to them -- possibly (though I didn't show it so) even blocking the sea route through. The land is shadowy, mysterious, and dangerous, so that could explain why nobody's eager to go past it. On the other side, Keetongu's island is populated by ginormous, intelligent, and dangerous Tahtorak land dragons. Perhaps they will attack any boat they see offshore (I assume they can at least wade out a little, though they probably wouldn't swim to another dome), so people could have similar issues with sailing that way.
And that's all I've got for now. Thoughts? Questions? Criticisms? More ideas?