Topics course. What did people think about the shape of our world before we knew it was a sphere? We will take a tour of mathematics related to this question, from the Egyptians and Babylonians to the present. The "possible" shapes of the world are now mathematically well understood. The question of the shape of the universe involves higher dimensional mathematical objects, and relates to the recently proved Poincare conjecture. First stated in 1904, it was viewed as one of the seven most important problems of the new millennium.