housands of people pass through the Green Street subway station every day, but few probably notice the art gallery on the outbound side of the ground-floor level. The Axiom art gallery, directly attached to the station, showcases experimental art that often incorporates digital media and other forms of technology—an exhibit inspired by mathematics, for example, featuring Wikipedia entries about mathematical concepts—and unique and daring shows such as “Art Cake,” which featured works of edible art. Exhibitions change often, so there is always something new. And unlike the pricey MFA or ICA, it’s free. Arpie and Moravek