  We present CO(J=1-0) observations in the direction of the Soft Gamma Repeater
SGR 1806-20 with the SEST telescope. We detected several molecular clouds, and
we discuss in this paper the implications of these observations for the
distance to the X-ray counterpart AX 1805.7-2025, the supernova remnant
G10.0-0.3 and the very luminous O9-B2 star detected in the line of sight. The
distance of SGR 1806-20 is estimated to be 14.5 +/- 1.4 kpc and this Soft Gamma
Repeater is very likely associated with one of the brightest HII regions in the
Galaxy, W31. The large size of G10.0-0.3 (25 x 38 pc) for a young supernova
remnant possibly powered by a central pulsar (AX 1805.7-2025) indicates that
G10.0-0.3 could be expanding in the very low density region produced by the
wind of the blue star.
