We present two-dimensional spectroscopy of the gravitational lens system Q2237+0305 (Einstein Cross) obtained with the INTEGRAL fiber system in subarcsecond seeing conditions. The four components of the system appear clearly separated in the continuum intensity maps. However, the intensity map of the C III] lambda 1909 line exhibits an arc of extended emission connecting the A, D, and B components. This result can be explained if, as is usually assumed, the continuum arises from a compact source <~0.05 pc in extent in the nucleus of the object while the line emission comes from a much larger region. A lens model fitted to the positions of the four compact images also accounts for the arc morphology. In the framework of this model, the region generating the C III] lambda 1909 emission would have dimensions of about 400 h-1 pc across. We interpret the observed arc as a gravitational lens image of the extended narrow line region of the source.