In the middle of the ground floor of the enormous Brass Light Gallery complex there is a large, mostly empty room. Its bare walls are made of pressure-cleaned cream city brick. The front of the room, which looks out on St. Paul Avenue, has been sectioned off by mirrors in ornate wooden frames. An extravagant cut crystal chandelier, along with a variety of other lighting fixtures, is reflected in the mirrors. So are the massive horizontal steel and concrete forms of the Marquette Interchange outside.