I had built one in our basement. In a outside corner I built a insulated room, about 3x3 with 2x4 and removed the sill insulation. The wood 2 walls I finished with osb and dry-locked the block. insulated the ceiling to keep the cold from getting up. My better half has had no complaints and have kept veggies from the garden well into winter/spring as well as all caned goods
I was always told to leave it with a dirt floor. A 4 inch PVC pipe to the outside for some air flow.
I dumbed into another storage location. At camp, there is a dug water well, I believe it's almost 20 feet deep. Water level is about 8 feet below ground level. On top is a cement slab, with a metal trap door about 2 feet square. I store potatoes ( about 300 lbs) and all my dahlia bulbs all winter by suspending them in sacks above the water. It's hard to believe, but the potatoes haven't sprouted at all. They're hard as rocks. Must be the exact temperature and humidity for ideal storage.