  The massive clump G10.6-0.4 is an OB cluster forming region, in which
multiple UC HII regions have been identified. In the present study, we report
arcsecond resolution observations of the CS (1-0) transition, the NH$_{3}$
(3,3) main hyperfine inversion transition, the CH$_{3}$OH J=5 transitions, and
the centimeter free-free continuum emissions in this region. The comparisons of
the molecular line emissions with the free--free continuum emissions reveal a
0.5 pc scale massive molecular envelope which is being partially dispersed by
the dynamically-expanding bipolar ionized cavity. The massive envelope is
rotationally flattened and has an enhanced molecular density in the mid-plane.
In the center of this massive clump lies a compact ($<$0.1 pc) hot
($\gtrsim$100 K) toroid, in which a cluster of O--type stars has formed. This
overall geometry is analogous to the standard core collapse picture in the
low-mass star forming region, with a central (proto-)stellar object, a disk, an
envelope, and a bipolar outflow and outflow cavity. However, G10.6-0.4 has a
much larger physical size scale ($\le$0.1 pc for typical low--mass star forming
core). Based on the observations, we propose a schematic picture of the OB
cluster forming region, which incorporates the various physical mechanisms.
This model will be tested with the observations of other embedded OB clusters,
and with numerical simulations.
