It is in Desert, about 90 steps west of the spot the map marks with that name.

And 5 down from the surface once you are there.

• 1 — Desert, as the map itself names it
• 2 — the ground above the treasure

• Key 3667: a locked door bars the way, and that is the number of the key that opens it.
• A rope. You drop in through a hole and a trapdoor, and a rope is how you climb back out.
• Something for banshee, dragon and orc berserker — they live down there.

The chest is 5 floors under the surface. Going down over it, this is what each floor uses:

1. Ground: down through stairs.
2. 1 down: down through stairs.
3. 2 down: down through a trapdoor.
4. 3 down: down through a hole.

• 1 — the way in: stairs, ground
• → — the treasure lies this way

• 2 — stairs, 1 down
• → — the treasure lies this way

• 3 — a trapdoor, 2 down
• → — the treasure lies this way

• 4 — a hole, 3 down
• → — the treasure lies this way

Some floors are not on the list: their way down is further off than the rest, and that stretch you have to find yourself.

• 1 — the chest

One chest, one reward.