The post notes that "collaboration and iteration are the keys to making good games," so with that in mind, we get to hear from a veritable legion of ArenaNet devs, each reporting on his or her role in the creation of the map. We hear from Jeff Grubb on the lore of the arena, we hear from Egan Hirvela on the process of map design, and Habib Loew tells us how the programmers make it work. Then it's up to designer Nick Mhley and his designers to say things like, "You know what's cool? When you shoot the [trebuchet] and blow stuff up. But you know what would be cooler? Blowing up even more stuff!" Outstanding.
Then Peter Fries, Scott McGough, and the rest of GW2's writers whip up some dialogue for the announcer and oversee the recording of the lines. Lastly, it falls to Shen-Ming Spurgeon, Mclaine Diemer, Tirzah Bauer, Chuck Knigge, and the rest of the team's visual and audio artists to bring the area to life with their super-artistic magics, followed by Tyler Bearce and the other folks in QA to make sure it works as intended.
Phew, what a crowd! At any rate, for the full, uncensored details on the process involved in bringing a map such as the Battle of Kyhlo to life, head on over to the ArenaNet blog.