I am no expert, but from what I learnt so far (I asked myself the same question), I came up with two options, and both require two versions of the tiles, one opaque and one transparent.
The first is to use opaque dynamic tiles on top of your transparent ones, the former disappearing via a lua script when you are in the right area. That would be area specific, which is great, and if you are patient enough, you could may be create some kind of fading animation with timers, different transparency levels of tiles and timers.
The second is brute-forcing your way : create your map, make a copy, replace the tiles with the transparent ones and place teleporters/create a script to teleport in and out the alternative map with no transition. Simpler, but if you have several areas like this near one another, they will all be visible at the same time, which is kinda weird.
I think you already came up with something, but let us say I'm thinking out loud ^^
The first is to use opaque dynamic tiles on top of your transparent ones, the former disappearing via a lua script when you are in the right area. That would be area specific, which is great, and if you are patient enough, you could may be create some kind of fading animation with timers, different transparency levels of tiles and timers.
The second is brute-forcing your way : create your map, make a copy, replace the tiles with the transparent ones and place teleporters/create a script to teleport in and out the alternative map with no transition. Simpler, but if you have several areas like this near one another, they will all be visible at the same time, which is kinda weird.
I think you already came up with something, but let us say I'm thinking out loud ^^