1) Technically the max map size is 128000 x 128000 x 128000, at least creating maps for the base game. Warzone has developed Wzmap, which apparently allows you to create much larger maps, but that's very specific. Also, the map size seems to vary between various Radiant versions, so, for example, GTK Radiant 1.5 only allows to create maps of 64000 x 64000 x 64000 units, while 1.3.12 (and I think 1.4 as well, but I'm not sure), allow to reach the grid boundaries before deleting everything beyond them. To be even more technical, I'm not sure if there's a limit to where you can travel - it's a technical detail that has been exploited on Lugormod servers to allow a very large space for flying ships. You can basically travel to a VERY far away point in any direction (I think we're talking about billion units, if not infinitely more, I can't remember right now) before the player's position in space "resets", as if it transported you to the other end of another map space. So for example, you travel to -2560000000, 0, 0, and the moment after you find yourself at 2560000000, 0, 0. You won't get back to the same point of the map if you reach the proper coordinates of the new map space. Weird sci-fi stuff. 2) As Noodle pointed out, you can have a surrogate of day-night cycle, but with the base lighting system it won't really look that good. An alternative would be using Rend2, where you can actually enable a skylight that can rotate creating an effective day-night cycle, but it's still pretty much experimental, and it won't look too great either. 3) You should be able to select the map patches in Radiant and texture them normally, unless you prefer to texture them in Blender and keep them. In that case, if .md3 export doesn't work (although you can always scale the terrain down so that it fits the limits of 512 units size and then scale it up again in Radiant), you can try to export it as .ase - which shouldn't have those limits, if I remember correctly. 4) The exported patchwork, with the proper texture, is indeed solid, although players and entities could clip through due to bugs. Models on the other hand will require either autoclipping (spawnflags 2) or manual clipping. Usually autoclipping a model is considered positively when dealing with terrain models and simple geometry in general. Edit: A quick in-game test shows that the map space seems to reset somewhere after 1 billion units. Not sure about the exact number, but that at least gives a lower boundary.