This paper discusses a classroom experience in which a group of prospective secondary mathematics teachers were asked to create, cooperatively (in class) and individually, problems related to Viviani's problem using a problem-posing framework. When appropriate, students used Sketchpad to explore the problem to better understand its attributes (e.g., knowns, unknowns, and restrictions) and model its solution. With support and guidance, each student was able to create at least one very interesting and good mathematical problem.