The Traveler's house in Kalm.
The Kalm Traveler is an non-player character in Final Fantasy VII. He can be found in the rightmost house in Kalm later on in the game and will accept trades with the player for three items that he is searching for. The items he is looking for are the Guide Book, the Earth Harp, and the Desert Rose. The Guide Book can be traded for the Underwater Materia, which lets the player fight Emerald Weapon without a time limit. The Earth Harp is won from Emerald Weapon and can be traded for Master Magic, Master Command and Master Summon Materia. The Desert Rose is won from Ruby Weapon and can be traded for a Gold Chocobo. After handing them in, the Traveler leaves the house to journey to parts unknown.
If the player uses a cheat or a hack to get more than one Earth Harp, the old man will continually give them more Master Materia unless the player has not picked it up already. If the player does not pick up the materia, it just bounces in the air instead of him throwing another one.