Pending on the size of the hive, one of the hives from the Guant's Ghosts (Vurndunium hive or some such? Verdun WW1?) are relatively small (like NYC/Tokyo/Mexico City/London size...well, probably of those added together) were they are sort of a play on today's cities, just once again on a more massive scale.
Some of these cities had a 40k equivalent to a medieval city/castle wall as well as a huge "force field dome" that would project up and cover the city from bombardments.
Then there are hives that the current population of earth could fit inside, with some amounts of ease pending size, and these I think are designed to be "larger than the imagination" where we cannot comprehend how VAST it actually is.
The best way for me to explain it would be to take your "downtown" or "commercial business district" or whatever it's called, and the surrounding area and multiply it by 1,000,000,000,000 (add or subtract the amount of zeros for own desire). I mean I personally view NYC as a "hive" since the idea that 9 million people living in that small of an area is not really imaginable for myself - it's a place that I see in movies, and is otherwise a dot on a map. Other people who live in highly dense places, hey look at those cities that I used as examples above, can reasonably see that better than someone who lives in a small town/city.
There could rather easily be a hive that on the "surface" or "top" is practically a green healthy looking area, because the actual "hive" is below, and if you don't look down travel there you will never know it existed; and the reverse is true.
No problem sir. I appreciate the multitude of views, but basically it comes down to the art and the novels not jiving with each other.
I am not sure if it is the fact that the "art work" and "novels"/"fluff" not gelling together, or if the artist's/author's take on the situation does not meet your standards. Like what Obi-Wan told us..."So what I told you was true... from a certain point of view."