How do I make a custom map size? (512x512 would be awesome.)

I think "HUGE" isn't huge enough. I want a map to be 512x512 (or 256x256 if my laptop doesn't have enough power.)

Is there a mod I must download to make customizing sizes an option? Thanks in advance.

This question comes regularly in the "Creation and Customization" part of the forum. This is a recent thread about it (forget about 512x512 and probably even 256x256).

Technically, the simplest is to create a Mod and to alter the iGridWidth and iGridHeight of the file Assets\XML\GameInfo\CIV4WorldInfo.xml. Note that a Grid is 4 tiles so the default values of Huge are 32x20 (128x80).

This said, some map scripts do not take their values from this file. For these mapscripts, you would have to edit the Python files in question.

Now what you could also do is to download a Mod made by Kjotleik who deals with bigger map sizes. Find his name in the users list and you will find his Mod.