Not sure which glowstone you're referring to - the ones in the middle by the glass window don't - although you do get your bubbles refreshed if you kiss the bottom, but that's just an illusion, and you soon start drowning. :S
There is a pillar of air created by the ladder in the nearest corner, which does let you get down to the bottom though.
If we want to do a 1:1 replica (or at least begin with something the right scale, even if the end result is nothing like it), we need an area at least 450x450 blocks. (I'd prefer 600x750 to include a bit of the surrounding area.)
For comparison, the swimming pool (building) is 100x100 blocks ( I'm assuming; I only counted roughly :P )
That's a pretty big area we'd need to clear - though unlike the swimming pool we don't need to dig all the way down.
Going ~16 blocks below sea level would be enough, though maybe a few more than that might look better.
So. Are people wanting to be doing that?
Also, do people want to aim for completion by 17th March (the tenth anniversary of full site opening), which basically gives us a week?
The whole Eden Project site is ~450m² - most of which is outdoor gardens and assorted buildings - the two biodomes are only about 1/6th of that space combined.
The reason for dropping 16 is:
a) to stop the tip of the big one from reaching cloud level and looking crap.
b) the site is an old quarry, so is actually in a dip in the ground anyway.
Technically, to be accurate, we should probably be around 30..40m above sea level, and then drop a certain amount down from that - but that's probably taking things a bit too far. :)
As right as possible, what with not having actual blueprints to follow. :)
Knowing the biodome heights along with width/length should give us a fair guide, but if we're going to do it I'll also try and track down heights of the other buildings/structures to make it easier.
I'm going to go hunt around for a suitable area (i.e. make sure it's not going to collide with anyone's structures, but also isn't too far) and then create a warp point there.
Once I've done that I'll put a central marker, and if you could start clearing ~200..250 in each direction from that marker that'd be great. :)