ffxiv guildleve:It's the Smell  

First of all, be aware that there is no fighting involved at all, you just have to run around the city and "Examine" boxes on the ground.
It says Rank 30, but feel free to do it as soon as you have 200 faction points and time to spare whatever your level and rank.

Reward:
Fluctuating, depending on whether you exchange it for some other completed leves, their level and on how many boxes you find as well.
I got around 60.000 gils, having exchanged 4 leves for rank 20 and collected all 12 boxes.
Also got 6 Faction Points for the Horn and the Hand.

(I also heard people speaking of rare items as reward, but never got one myself. Please add whatever you got if you want to)


Walkthrough:
1.Go to the City of Gridania's Aetheryte and "activate" the Levequest.
2.It says you have only 10 minutes, but I was able to complete it under 5 minutes including the blah-blah and picking up all boxes so don't worry about the timer.
3.Diego Athral (NPC) will pop behind you, speak to him to activate the quest.
4.It will show 4 yellow areas in the city, simply go there and "Examine" all the boxes you find in the area.
5.I found usually between 2 and 4 boxes in each area.
6.Once you picked up all boxed in the same area, the yellow circle will disappear, so just proceed to the next area on your map and do the same.
7.Once you have collected all boxes (12) go back to Diego and talk to him to get your rewards.