  We present multi-frequency radio continuum VLBI observations of the
gravitational lens system B0218+357 carried out using a global VLBI network and
the VLBA. The source has been observed with resolutions from 0.2 milliarcsec to
5 milliarcsec and displays interesting structure. The spectral properties of
various components show that the lensed object is a standard flat spectrum
radio source which has many self-absorbed components. Based on the flux ratio
of the lensed images as a function of frequency we propose a simple model for
the background radio source.

Astrophysics