  In the context of the study of the size-age relationship observed in star
clusters in the Large Magellanic Cloud and the investigation of its origin,
here we present the determination of the structural parameters and the
dynamical age of the massive cluster NGC 1835. We have used a powerful
combination of optical and near-ultraviolet images acquired with the WFC3
onboard the HST to construct the star density profile from resolved star
counts, determining the values of the core, half-mass and tidal radii through
the comparison with the King model family. The same data also allowed us to
evaluate the dynamical age of the cluster by using the 'dynamical clock'. This
is an empirical method that quantifies the level of central segregation of blue
stragglers stars (BSSs) within the cluster half-mass radius by means of the A+
parameter, which is defined as the area enclosed between the cumulative radial
distribution of BSSs and that of a reference (lighter) population. The results
confirm that NGC 1835 is a very compact cluster with a core radius of only 0.84
pc. The estimated value of A+ ($0.30\pm 0.04$) is the largest measured so far
in the LMC clusters, providing evidence of a highly dynamically evolved stellar
system. NGC 1835 nicely fits into the correlation between A+ and the central
relaxation time and in the anti-correlation between A+ and the core radius
defined by the Galactic and the Magellanic Cloud clusters investigated to date.
