About This File
It has custom textures, lots of place to build, a coast all around for placing ports (or blueprints built on water, like the Alcatraz or oil platform), and fertility everywhere. The Tropical Island version also has oil everywhere. Both have a fair bit of vacation areas from the start. Like the default islands, it has no road or rail connections anywhere, so you WILL need ports and airports.
It has no ground water by default in the normal game, just like the normal island, BUT if you use Neidhard's resource enabler ( http://www.file-upload.net/download-2360525/mod_requied-for-new-maps.rar.html ) then you'll have underground water reserves everywhere too. It's up to you exactly how much you want to cheat, basically. Personally I'd think an island would get plenty of rainfall to have water for its people, but you can also take it as just a desert island and import your water if you prefer it that way. Or you can use the sandbox mod buildings to give you water.
The same resource enabler will also give you oil everywhere on The Two Sisters replacement map, if you use that version.
Either version is a flat and gently rounded square, almost perfectly flat in the middle, and gradually curving down towards the shore line, to meet the water in a gentle slope. It's still more than flat enough to build on in any point.
It is not based on the altitude data of any real place. It's just an artifficial island with as much place to build as possible, while not having any hard corners or perfectly straight edges, so it basically still looks somewhat natural. If it helps, you can imagine it as an artifficially built island, like Dubai has been building, except bigger.
There are no trees in water, nor in fact even on the beach.
I have reduced the ground texture and shadow map to 2048x2048, down from the default 4096x4096, since it seems to run smoother on my computer that way and it's not like a flat map really needs more detail. And the game's terrain multi-texturing makes it look ok up close too anyway.
To install, just unzip one or both .patch files from the .zip file into your Paks folder. To uninstall, just remove it. (Removing it might, however, break any cities built on the custom map.)
IMPORTANT NOTE 1: No attempt has been made to match the height of the map it replaces, and arguably it's not even possible to both have two maps have the same height in any place AND have one be flatter than the other. I.e., it might or might not break existing cities built on the island it replaces. It is highly recommended that you start a new city if you want to use it.
IMPORTANT NOTE 2: It has only been tested with Cities XL 2012. I have no idea if it works with 2011 or any other version.
Note 3: yes, I know it's not some great achievement. It's not the best map out there, nor particularly hard to make, nor the most realistic, nor anything else. I just wanted a flat map to build a great big island city on. Maybe someone else can use it too. Or maybe not.