The Civilization III file structure
Civilization III scenarios are saved in BIC (Binary Interchange Code) files that contain game rules and the scenario’s map. This allows mod creators to easily distribute their scenarios and maps.
The default Civ III rules are stored in a special, read-only file called civ3mod.bic that is stored in the root game install directory. We strongly recommend that you not edit the civ3mod.bic file, as it is used when playing non-scenario games and changes to this file can dramatically unbalance the game. The editor also uses the civ3mod.bic file to establish the default rules when creating new scenarios.
If you alter the civ3mod.bic file, the only way to restore the default rules is to reinstall the file from your game CD.