I have attended many seminars on exercises on the development and reduction of muscles to ensure a balanced muscular development to prevent muscular and skeletal injuries. Mega calves are beautiful to so many people and you can build them by low rep high with heavy weights or you may be overweight or you may just be lucky or unlucky to have the genes. The good news is that you can reduce your calves muscles by exercise and if overweight, by weight loss.
For exercise bicycling in a gym is excellent and the best is "spinning", this is a high rpm cycling with little reistance which you should do for 30-60 minutes within your aerobic capabilities. Watch TV while you do it, or if you want fun there are so many spinning studios in Health Clubs that have a party atmosphere. Losing calf muscle is perhaps one of the hardest to lose but if you diligently apply yourself it will be successful.
Finally, just as a mention only, as I'm not in favor of this. In Korea they have a surgery that can reduce calf muscles and I have seen the excellent result.