Looking in the editor, I see numbers by Citizen and Building for Defensive Bonuses in General Settings. Previously, I had the impression that another building or citizen wouldn't change any of the defense bonuses. Do the numbers mean that each additional building gives the city a +16 % defense bonus, and + 16% for each citizen? For example, according to that information, a size 1 city with a fortified spearman on flatland, has defense of 2 + (.5 x 2) [for the town] + (.25 x 2) [for fortification] + (.1 x 2) [for flatland] + (.16 x 2) [for the 1 citizen] = 2 + 1 + .5 + .2 + .32 = 4.02. But, if the city is size 2, that spearmen has a defense of 4.44 if I've read that right (the civ III combat calculator assumes equal sizes of cities and no buildings). If it's a capital it has at least one building, so it would have at least .32 more defense for the spearmen.