  HST V and I-band observations show that the gravitational lens B1359+154
consists of six images of a single z_s=3.235 radio source and its star-forming
host galaxy, produced by a compact group of galaxies at z_l = 1. VLBA
observations at 1.7 GHz strongly support this conclusion, showing six compact
cores with similar low-frequency radio spectra. B1359+154 is the first example
of galaxy-scale gravitational lensing in which more than four images are
observed of the same background source. The configuration is due to the unique
lensing mass distribution: three primary lens galaxies lying on the vertices of
a triangle separated by 0.7 arcsec (4/h kpc), inside the 1.7 arcsec diameter
Einstein ring defined by the radio images. The gravitational potential has
additional extrema within this triangle, creating a pair of central images that
supplement the ``standard'' four-image geometry of the outer components. Simple
mass models consisting of three lens galaxies constrained by HST and VLBA
astrometry naturally reproduce the observed image positions but must be
finely-tuned to fit the flux densities.
