What is the Old Sea Map?

The Old Sea Map is a key item in Pokémon Emerald that charts a course to Faraway Island, a place that appears on no in-game map, where a wild Mew, the first generation's phantom, can be found roaming a small meadow. In a generation where Mew otherwise existed only as a transferred relic or a cheat, the map was the only legitimate way to catch one.

It was distributed for the Japanese version of Emerald, principally at Pokémon Festa 2005, the summer tour that ran from July 17 to August 21, 2005, and at PokéPark that September; Taiwan received it for the Japanese version the following year. The number of holders is put at about 25,800, against Emerald's millions of owners.

It was never distributed for the English or any other language version of the game, a point Bulbapedia states outright. No Western Emerald, whatever its label promises, can sail to Faraway Island through any legitimate means, and the island's Mew remains bound to the Japanese cartridge, wherever in the world the map was handed out.

As an object, the Old Sea Map is invisible: a flag in a save file, set by a download station at a summer festival. Its rarity is the purest of the era, a famous place that exists only in cartridges that were in the right country in the right six weeks of 2005.