  High-resolution Hubble Space Telescope optical observations have been used to
analyze the stellar population and the structure of the poorly investigated
bulge globular cluster NGC 6316. We constructed the first high-resolution
reddening map in the cluster direction, which allowed us to correct the
evolutionary sequences in the color magnitude diagram (CMD) for the effects of
differential reddening. A comparison between the CMDs of NGC 6316 and 47
Tucanae revealed strikingly similar stellar populations, with the two systems
basically sharing the same turn-off, sub-giant branch, and horizontal branch
morphologies, indicating comparable ages. The red giant branch in NGC 6316
appears slightly bluer than in 47 Tucanae, suggesting a lower metal content.
This has been confirmed by the isochrone fitting of the observed CMD, which
provided us with updated values of the cluster age, distance, average color
excess, and metallicity. We estimated an absolute age of 13.1 $\pm$ 0.5 Gyr,
consistent with the age of 47 Tucanae, an average color excess E(B-V) = 0.64
$\pm$ 0.01, and a true distance modulus (m-M)0 = 15.27 $\pm$ 0.03 that sets the
cluster distance at 11.3 kpc from the Sun. In addition, the photometric
estimate of the cluster metallicity suggests [Fe/H]$\approx$ -0.9, which is
$\sim$ 0.2 dex smaller than that of 47 Tucanae. We also determined the
gravitational center and the density profile of the system from resolved stars.
The latter is well reproduced by a King model. Our results confirm that NGC
6316 is another extremely old relic of the assembly history of the Galaxy.
