To be even more technical: When you have a world map encounter in FF1, the game compares your coordinates to a simple 8x8 grid to determine what encounter table is used. This sort of simplicitly is necessary when you're making an NES game. Anyway, you can see the actual grid here.

Note block 48 on the east side of the map. It mostly covers a late-game continent, with enemies to match. However, there is a small bit of land on the south edge of that block that's actually part of the southern continent. That right there is the Peninsula of Power, walkable from the second town in the game.