To the north is all mountains, to the south is the TPU, to the east is the pyramid, so all that really leaves is west. Here's some possible locations:
A) Lots of room to work but can't be seen by spawn. I think it would be interesting for people to approach the TPU to see the logo behind it.
B) It's close but it is off center quite a bit.
C&D) Probably my favorite locations. It is pretty likely both can be at least partially seen from the park and tree farm. C is almost on center to the spawn and will be accessible by the park. Unfortunately, a large hill would obscure a lot of it and the same goes for D. D is good because there is likely to be a major path leading that way anyway.
Edit: C&D have very, very large hills between them and the spawn. They are probably not the best choice.
E&F) I really don't like because of the 45 degree angle to the spawn. You gotta do a lot of running to look at it head-on. The advantage though is not much is out that way.
G) Is another good location because of it's almost perpendicular location to the spawn. The only problem is that it is quite a ways away.
I would also highly recommend reducing it to 4 deep (the minimum you can fit a stair well in) instead of 8 or 10 to conserve on time and resources. Could even drop down to 3 with ladders.
On to less serious matters...
I made Peter the Creeper more anatomically correct but, it could be even more correct except wool, cactus, and glowstone are in short supply:
And I present a really, really big tree (natural):
