  We present the first results on the Dalitz-plot structure and improved
measurements of the time-dependent CP-violation parameters of the process $B^0
\rightarrow K^0_S K^0_S K^0_S$ obtained using $468\times10^{6}$ $B\bar{B}$
decays collected with the BABAR detector at the PEP-II asymmetric-energy $B$
factory at SLAC. The Dalitz-plot structure is probed by a time-integrated
amplitude analysis that does not distinguish between $B^0$ and $\bar{B}^0$
decays. We measure the total inclusive branching fraction ${\cal B}($B^0$
\rightarrow K^0_S K^0_S K^0_S)=\rm (6.19 \pm 0.48 \pm 0.15 \pm 0.12)\times
10^{-6}$, where the first uncertainty is statistical, the second is systematic,
and the third represents the Dalitz-plot signal model dependence. We also
observe evidence for the intermediate resonant states $f_0(980)$, $f_0(1710)$,
and $f_2(2010)$. Their respective product branching fractions are measured to
be $\rm(2.70\,^{+1.25}_{-1.19} \pm 0.36 \pm 1.17)\times 10^{-6}$,
$\rm(0.50\,^{+0.46}_{-0.24} \pm 0.04 \pm 0.10)\times 10^{-6}$, and
$\rm(0.54\,^{+0.21}_{-0.20} \pm 0.03 \pm 0.52)\times 10^{-6}$. Additionally, we
determine the mixing-induced CP-violation parameters to be ${\cal S} =
-0.94\,^{+0.24}_{-0.21} \pm 0.06 $ and ${\cal C} = -0.17 \pm 0.18 \pm 0.04 $,
where the first uncertainty is statistical and the second is systematic. These
values are in agreement with the standard model expectation. For the first
time, we report evidence of CP violation in $B^0$ \rightarrow K^0_S K^0_S
K^0_S$ decays; CP conservation is excluded at 3.8 standard deviations including
systematic uncertainties.
