  Submilliarcsecond astrometry and imaging of the black hole Sgr A* at the
Galactic Center may become possible in the near future at infrared and
submillimetre wavelengths. This resolution is sufficient to observe the
silhouette the supermassive black hole in the Galactic center casts upon
background emission. However, more exciting is the prospect of observing ``hot
spots'' in the accretion flow. Here we discuss how such measurements may be
used to test not only the consistency of General Relativity, but also the
validity of the Kerr metric in particular.

Astrophysics