This is the Diakon radish. It is the biggest radish I have ever seen! It is strong flavored and has lots of edible mass. Diakon radishes are a great cover crop(or companion planting) for future plantings because the root digs deep down in the soil to break it up and bring up nutrients for smaller rooted plants. Farmers will plant them as a cover crop in the field during the growing season and let them dye down over winter. Using diakon radishes in this way can eliminate or lesson the need for deep tilling.
Be sure to try one if you have a chance.