Driving across the recently rebuilt I-35W bridge in Minneapolis, one may notice what appear to be fluid-looking sculptures rising up from the concrete center median. In fact, the structures — shaped like the international symbol for "river" — are pollution-control devices, cast from concrete that actually catalyzes oxides of nitrogen and carbon monoxide using the UV rays from sunlight. The pillars work in a fashion similar to the automotive catalytic converter, but at a much lower temperature. Made from photocatalytic concrete produced by Cemstone, the material has the added benefits of remaining bright white thanks to the catalytic process, and converting pollutants into salt — good for keeping snow and ice melted off the bridge during the 11-month Minneapolis winter. [KSTP via PopMech]