  W49A is one of the most luminous giant H II (GH II) regions in our Galaxy.
This star forming complex contains numerous compact and ultra-compact (UC) H II
regions, extending over an area of 15 pc. It emits about 10^{51} Lyman
continuum photons per second, equivalent to the presence of about 100 O stars,
but it is completely obscured in optical wavelengths by intervening
interstellar dust. The center holds a ``cluster'' of about 30 O stars, each
within an individual UCHII region emitting free-free emission at cm
wavelengths. Our deep K-band (2.2 um) image toward the W49A cluster reveals
just two of the individual exciting stars, each associated with a point--like
radio source, but the rest are invisible. These O stars are so recently born as
to not yet have emerged from their natal dust cocoons, in contrast to other
Galactic clusters embedded in GH II regions in which many of the individual
massive stars are already revealed. Plausibility arguments are made which
suggest that a stellar disc might be common during the entire UCH II phase of
massive star birth, as it persists after accretion ceases in some stars.
Nebular emission (e.g., from Br gamma) is visible around the periphery of the
central region of W49A, along with candidate exciting stars. Star formation
there may have preceeded that in the center, or its lower density environment
may have speeded up the dispersal of the natal dust cocoons. The W49A cluster
can serve as a template for the more luminous buried star clusters now being
found in normal galaxies and starbursts.
