  The color-magnitude diagram of $ \sim 3 \times 10^5 $ stars obtained for
Baade's Window towards the Galactic bulge with the OGLE project reveals a
surprisingly narrow main sequence due to galactic disk stars at a distance of
$d \sim 2 $ kpc, i.e. at the location of the Sagittarius spiral arm. A more
careful analysis indicates there is an excess in the number of disk stars by a
factor $\sim 2$ between us and $d \sim 2.5$ kpc and a rapid drop by a factor
$\sim 10$ beyond that distance. It is unlikely that the observed structure is
an artifact of the interstellar extinction, but careful determination of the
extinction is needed before the structure is firmly established. The narrow
main sequence extends down to stars as faint as $M_{_V} \approx 7$, i.e. it is
composed of old stars. This is not expected in a conventional disk model, or in
a conventional model of a spiral structure. However, a strong concentration of
old stars towards spiral arms has been noticed in some other galaxies, like M51
(Rix \& Rieke 1993), with the near infrared surface photometry. We have also
found that the relative distribution of red clump and red giant stars in the
Galactic bulge implies that there is a relatively young stellar population
present there.
