As an open game, the term "level" for a self-contained chunk of gameplay is meaningless to Exon but... eh... I'm already using "Area" for something else. Either way, it's time to build more of them! Blog 815: The Next Level
Regarding WC3 v1.13, another way to play this version could be to download from Blizzard's servers the free v1.27a digital version. And then you can downgrade it to 1.13 with a third-party downgrader.
These third-party downgraders each have their own specific merits and downfalls. afaik none of them will give you an exact binarily identical set of folders and files, especially when compared against a properly upgraded 100% official WC3 game. But hey, neither is the official v1.27a digital version to begin with when compared to a genuine 1.27a. The reason is, this version is an "a2" version, despite the full version number being identical to the one for v1.27a