The ISS with its 73m x 108m Integrated truss structure, apparently, is the largest (by dimensions) artificial object in space.
I know about the Krab experiment which produced two self assembly rings of 20m diameter, attached to a Progress spacecraft. That gives 40m x 20m.
Both Space Shuttle orbiter and Mir station were a bit shorter than 40m.
The Inflatable Antenna Experiment's struts were shorter (28m) too.
So the question is: have there been any (other than ISS) artificial objects longer than 40 meters in orbit?