Questions About the Engineer 'City'

First off - how awesome do these images look?  Worth the wait I reckon :) 

Looking at the cityscape though it does pose some very interesting questions about the engineer culture.  I'm guessing the central courtyard area (which iirc Big Dave worked out was about 3 km across) is so large as it needs to accommodate ships.  We see one opening in the centre but could there be more?  We also see a large scorpion like ship - but whether that is from paradise or elsewhere is unclear.  The inhabitants certainly look curious, confused/angered even, by what's arrived . . .

But is that the only reason?

 We see a high wall around the central arena that has several pathways to what appear to be gated entrances/exits.  There is also a pathway up to the large dome (which again BD reckons is about 1 km across).  

The scale is huge.  Behind these walls are what looks to be skyscrapers and other assorted buildings.  Much like we may see in places on earth; housing etc seems the likely purpose.  I'm estimating the size of the city, as a whole, to be something similar to Amsterdam or other relatively small city?

It would seem then that the inhabitants live away from the central area behind what could be interpreted as defensive or protective walls.  If that's the case, what are they protecting from?

It reminds me of the Rome Colosseum but on a much larger scale, and we all know what happened there . . .

Is this central area used regularly or is it reserved for special arrivals from other engineers or members of the civilisation from afar?  Perhaps even more advanced or beings higher up in the chain, as it were?

It could be as simple as this area being the space port!  Perhaps all engineer habitats follow this pattern?  We have seen their ships take off (landing would be similar, right?) and know they go straight up, so given they are a space fairing race then 'parking' their vehicles would be a pretty big deal and fit what we see here . . .

Whatever it is though it is clearly an important area and one that they give huge attention to.  Given that many think the Hall of Heads is in the big temple, and they could show great beings from the past, perhaps this whole set up is to honour and worship their creators who still come from the skies?  Maybe this is where we humans from earth rebelled and wanted to 'go our own way'; which may have prompted the failed attempt at our 'introduction' to the black goo?

It also makes me wonder, and I doubt we'll get to see this, if there are other cities/places like this on Paradise, and if so, has the infection reached across the whole planet yet?

Lastly, where have all the bodies gone in the last pic?  Have I got it wrong or do we see many images with the corpses but then see this image where they aren't present?  How could that be?  Unless this image is prior to David's arrival or I'm just not seeing them due to scale?

So, a lot of questions but would be happy and interested to hear your thoughts and ideas on them, or any others that you have re. the engineer city.  Some if not all - lol, have probably been answered elsewhere; if so, apologies, point me in the right direction and please ignore my ramblings :)