In GlobalDefines.xml there is a value called CAMERA_CITY_ZOOM_IN_DISTANCE which is normally set to 3500.
You might try setting it to something like 4500 and see if that helps. Then you can try other values to get a good setting, if 4500 doesn't quite solve the problem but does help . If it doesn't help, then this is not the correct setting to adjust, but it probably is.
You also should not modify the original file, for a variety of reasons. An easy option is to change a copy you have put into the XML folder in the Custom Assets folder located in some place like My Games\Beyond the Sword\CustomAssets. The other option is to make a mod, although that has two problems:
First, creating a mod that you have to load just to get one single change seems excessive.
Second, the mod would only be in effect when running that mod whereas the Custom Assets solution will be in effect even if you run other mods that do not specifically exclude using custom assets.
On the other hand, the Custom Assets version will tend to override any settings that are done in a mod that includes this file (some mods may change settings in this file, without which the mod will not work correctly). There is a second file that serves the same purpose called GlobalDefinesAlt.xml (regular BtS doesn't use this, but some mods do). If issues arise, you can move just this one setting into this alternate file (don't forget the initial lines with the "?xml" tag and "Civ4Defines" tag at the beginning, and the closing "/Civ4Defines" tag at the end) and remove the GlobalDefines.xml from Custom Assets. But, of course, some mods use both files - for these you'd probably need to go in and make the change in the mod's GlobalDefines.xml file and set it to ignore custom assets if it doesn't already (in the mod's .ini file).
