Re: WoW gold limit reached
There's also GM isle... And yes, as to that place under the city, and also old IF; I've known some who have claimed to get there.
Wrath of the Lich King is where this will really come up. Because being told "no" to flying mounts in lvl 80 areas won't go without a reaction. But yes, there are places where it's obvious they took graphical shortcuts in the original content; largely because they never envisioned it becomming an issue.
In fact, the whole issue of flying mounts didn't even arise until other MMORPGs had them, then it became a matter if some claimed it as a feature, others had to accomodate due to business issues relating to their competitors.