Swiss cheeses include many variations that reflect differences in taste, sharpness, density (dryness), the size of the characteristic holes throughout the cheese, and the overall delicacy or robustness. THE HOLE TRUTH . . . Ever wonder where the characteristic holes in Swiss cheese come from? They form as the cheese ripens. Carbon dioxide gas produced during the natural fermentation process becomes trapped inside the cheese curd. And voila! These pockets of gas form the famous Swiss cheese holes.