On the Grand River in Cambridge, Ontario, a glimmering glass addition by Toronto-based firm RDHA brings a flamboyant edge to the former Galt Post Office, an early 19th-century heritage building that had sat vacant for nearly a decade. Seeing an opportunity to revive the structure, the city’s public library system acquired the site, with plans to create a place dedicated to “makerspaces,” as opposed to a conventional book facility. To accommodate an ambitious program—which includes video- and sound-recording studios, a black-box theater, and rooms with equipment such as woodwork and metalwork machines, laser cutters, and smart tables—the architects had to create 20,000 square feet of space. But the site had many constraints, due largely to its location against a flood wall, so the team inserted two volumes that cantilever out over the water. Clad in glass, fritted with patterns alluding to decorative elements of the historic post office, the addition provides views onto the old building as well as the river below. Although the resulting “library” lacks books, what it offers is an invaluable service: endless possibilities to create.