Where is the entrance field in sonic unleashed

Well.. on the map, there is a place that should say "new"(located on the top middle part of the map (if you know what I mean). It's the place that you can collect sun and moon medals. If you want to reach Tails, then enter the moon door (where it's night and Sonicl turns into a werhog), and finish the misson. After, you will there meet Tails and explore two new more places. Hope this helped!