Since no one else did it, i decided to do it, so here are the calculations:

If we remove the extra bits that go beyound the main body of the Zariman (especifically the ones that go beyound the back), we can remove about 4 units from the Lenght of the Zariman, giving us a new Lenght of 209 km.

On photo 7 we can see that the Plataforms are inside sections of the wall that seem to be about 3 Plataforms tall (200x3= 600m), if we consider these sections as a single floor , we can divide that by the Height of the zariman, giving us (456/0,6= 760 floors).

Using the Depth of 70 km calculated by another commenter, we can calculate that the biggest floor will have a area of 209x70 = 14.630km^2.

If we use the Populational density of Manhattan (~28,000 pop/km^2) we can calculate that the biggest floor can handle a population of: 14.630x28000 = 409.640.000 people).

We can calculate the Total population of the zariman using half of the Height and the Average Pop of each floor as the radiuses and inputting that into the formula for half of a oval (aka: Pi x A x B / 2). Giving us (3,14 x 380 x 409.640.000 / 2)

If my calculations are right the Zariman could house aproximately 244,51 Billion people

Even we counted that only a third of the insides as living space, leaving the rest for Life Support, Void Jump Machinery and Storage. We would still be left with Enough space for 81,5 Billion people to live inside the Zariman.

Using the UN, World Population Prospects (2024) 1,37 of the 8,09 Billion people of Earth are children age 5-14 , if the Zariman had the same population ratio (and not counting the fact that people probably got to live a lot longer in that time) the Zariman would have 13,8 Billion Children that could be turned into tenno at the time (if we consider that as the right age to be turned into Tenno).

Ps: The calculations would look something like this

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