Mathematics and art have a connection that goes far beyond proximity. In fact, they are two symbiotic areas shaping a beautiful, logical, systematic, and breathtaking world. One of the works that exposes their intrinsic connection, in a clear, rigorous and simple way, is the book Beautiful Geometry by Eli Maor and Eugen Jost. To a greater or lesser degree, we all feel the power that art exerts on our minds, both at a sensory and at a cognitive level. In fact, art is one of the privileged areas for the emergence of creativity. Combining beauty with rigor and reason, and based on the book mentioned above, we designed a professional development course for mathematics teachers, following a STEAM approach. The description of this course, illustrated with part of the graphic/artistic material produced by the participants, is the main object of this paper.