I would go about describing in English how it is you should be able to describe your map. For example, is there going to be a hard-coded set of N areas each with a set 16x16 tiles? Or, are you going to be more dynamic (allowing a player to build a city, thus changing the tile)? Obviously, the solution is different in each case. Once you've determined the parameters for what your map-description needs to be able to do, then the solution should be relatively obvious.

Almost always, design is driven by requirements concerns. More than that, it's often discovered as a logical conclusion from the requirements. Sometimes, the only logical conclusion from the requirements. If you're casting about for a good design, make sure your requirements are solid first. If they're not (and they usually won't be), fixing them will help solve your design problems.

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We are the carpenters and bricklayers of the Information Age.

Don't go borrowing trouble. For programmers, this means Worry only about what you need to implement.