  We present a study of a very peculiar object found in the field of the
cluster-lens Abell 370. This object displays, in HST imaging, a spectacular
morphology comparable to nearby ring-galaxies. From spectroscopic observations
at the CFHT, we measured a redshift of $z=1.062$ based on the identification of
[O ii] 3727 \AA and [Ne v] 3426 \AA emission lines. These emission lines are
typical of starburst galaxies hosting a central active nucleus and are in good
agreement with the assumption that this object is a ring-galaxy. This object is
also detected with ISO in the LW2 and LW3 filters, and the mid Infra-Red (MIR)
flux ratio favors a Seyfert 1 type. The shape of the ring is gravitationally
distorted by the cluster-lens, and most particularly by a nearby cluster
elliptical galaxy. Using the cluster mass model, we can compute its intrinsic
shape. Requiring that the outer ring follows an ellipse we put constraints on
the M/L ratio of the nearby galaxy and derive a magnification factor of 2.5
$\pm$ 0.2. The absolute luminosities of the source are then $L_B = 1.3 \
10^{12} L_{B \odot}$ and $\nu$ L$_\nu \simeq 4. 10^{10}$ L$_\odot$ in the
mid-IR.
