My cat Coco has turned twenty this year and is doing well but she really feels the cold. She has a basket she sleeps in with a heated pad under the blanket but that is not enough with a very cold autumn upon us. So we have built her cat cave around the basket as we did last year. It is just a cut-out cardboard box with a quilt on it for insulation. She has been as happy as.... since we put it together for her.