Time Dilation Chamber

By focusing on an area of at least 100 square feet that is unoccupied within 40 feet for ten minutes you can create a small box like structure with a single door. This Structure takes up 100 square feet on the outside but contains 2,500 square feat of space on the inside. The structure can't be destroyed or suffer any damage by non magical means. If Dispel magic or Antimagic field is cast on the structure the structure slowly fades out of reality while anything that was inside slowly fades back into reality in the nearest unoccupied space. While the structure is in existence and the door is shut time moves 10 times faster inside the structure then it does outside the structure. The spell last for 24 hours or until dismissed by the caster. Upcasting this spell increases the amount of time dilation occurs inside the structure.