Your world is unique to you and you alone. A place you retreat to in your dreams, imagination, and/or a fantasy land of perfection: a safe haven. Describe the flora and fauna your mind created, the weather patterns, food, all the things you made for yourself. This world is flawlessly built from your thoughts, but it has to have a twist. Perhaps the reason you created this land was for a villainous reason, maybe you have created something without consequence, or somehow this world is seen through the eyes of trauma. Whatever you can think of, create it. Just remember to describe things in perfect detail, make a glorious unforeseen twist, and have fun.