The Vault City designer notes is a holodisk in Fallout 2. It credits the developers of the game.
Location
The holodisk data can only be acquired by direct download to your Pip-Boy from the main computer in Vault 8 after defeating the inhabitants of the oil rig (it's the "talking" terminal in the eastern portion of level 3 of Vault City's vault, the same computer that provides the location of Vault 15). You will then see "Vault City Designer Notes" in the "Status" section of your Pip-Boy.
The computer referenced toward the end of the designer notes is in the northwest, or upper left, area and will provide 20000 XP each time it's used.
Transcription
Vault City went 
trough many incarnations. It was designed by Leonard Boyarsky, Jason Anderson, Feargus Urquhart, and Chris Avellone. Scott Everts built the maps, and the brave men who scripted this architectural Frankenstein were Rob Hertenstein and Dan Spitzley. And finally, Eric Pribish nearly gave his life testing the monstrosity that is Vault City.
Chris would like to thank the following people who helped during the production of Fallout 2: A Post Nuclear Role Playing Game:
Rob, Scotty, and Dan (of course), Eileen Suh, Sarah Smart, Emily Yance, Thuy Dang (who I never thank for anything), Chris Wright, and Tim Winkle.
Scotty would like to thank the following people:
Don & Aileen Everts and Avis Andre. And thanks to Bill Bridges for all the cool Fading Suns books!
Dan would like to thank the following people:
Split Enz for the great tunes, James Cameron for True Lies, Joe Viskocil for his kick-ass explosions, Chong's at Triangle Square for keeping me fed, Carlos Kotkin for finally taking the plunge (you'll be seeing the premiere of his first feature film any day now), on Land for the entertainingly unlikely Blaine McCracken novels, Red Dwarf for laughs, and finally, as always, Mom and Dad for bein' cool.
Rob Hertenstein would like to thank the following people:
Becky Warner (still trying to keep me out of trouble), Billie Ryder (for keeping me sane throughout this project), Little Ryder (who is supposed to arrive at the same time this game does), and Nicole Roman (for being there).
Eric Pribish would like to thank the following people:
Tommy Hood, Jr., Joe Isip and Julio Mata for not disowning me when I had to ditch out on D&D. To my old friends Brad and Dave Carnes for keeping in touch (all these years). Lastly, but most important, I would like to thank my loving girlfriend Rhonda Lauffer for understanding all the long nights and weekends when work took me away and for always being there for me when I came home.
As a reward for defeating the Enclave, Chris, Scotty, Rob, Dan, and Eric would like to take this opportunity to tell you to go to the computer terminal in the upper left corner of this level and use it.
Congratulations on saving the world. And thanks again for playing Fallout 2.
Notes
The disk is required to use the computer terminal described in the disk. Perception 7 is required to detect the plug in on the computer; it is not necessary, having spotted the plugin, to download the Vault City travel notes.