Treasure Map I is found in the Arcane Library, just to the west of the Pentagram Dome on Level 1, The Sorcerer's Labyrinth.
I've play-tested the dungeon's first level all the way through, but as I'm running an open-table game, I've had multiple groups go through parts of it three, if not four times.
The Arcane Library has what's very likely the first "big score" of treasure players will find in the dungeon.
So, it's of note that this map is given to players very early in the game—most likely the first session.
For the first level, I wanted to increase player agency for when they choose their directions at intersections between blind passages—a common occurrence.
In order to make informed decisions—to have agency—players who enter a new, large, labyrinthian dungeon like The Sorcerer's Labyrinth will need at least some sort of information at nearly every turn. Otherwise, it's just "Left or right? Who cares. Flip a coin." Or, "Left for loot!"
As intended, this is a very maze-like dungeon, and there's only so many "Left or right?" hallways you can add distant torchlight, wall graffiti, foot prints, whispers, chitters, glowing eyes, blood spatters, spider webs, broken daggers, orc dung, etc.
Giving a map straightaway increases player agency giving them points of interest rather like town rumors, a win-win in my book!
