Ann Arbor has a long tradition of what might be called “people’s art”: outdoor pieces that are often ephemeral and anonymous and sometimes literary or intellectual in nature. Aside from the predictable graffiti, we have had stone cairns in the river, fairy doors downtown, mowed designs in vacant lots, messages woven into chain-link fences, sidewalk chalk art, yarn-bombed trees, and stenciled fruit on bridge railings.

The cover of this month’s Observer depicts two truncated octahedrons made out of snow that appeared on Argo Pond last winter. They were the work of Hamlet Construction owner Robert Marshall, who made a number of the forms around town as part of what he calls the Hedron Project–using massive, whimsical objects to promote math literacy.

Marshall made snow sculptures using a hinged wooden mold. He’s also made a twenty-faced icosahedron that can be spun and climbed, and he is working on using a 3-D printer to make a twelve-sided toy dodecahedron. Ultimately, he hopes to create a math curriculum incorporating the structures for use in schools.