  We present the results of an unbiased $^{12}$CO/$^{13}$CO/C$^{18}$O ($J$ =
1-0) survey in a portion of the third Galactic quadrant (TGQ): $l$ = [219.75,
229.75]$^\circ$ and $b$ = [-5.25, 5.25]$^\circ$. The high-resolution and
high-sensitivity data sets help to unravel the distributions and physical
properties of the molecular clouds (MCs) in the mapped area. In the LSR
velocity range from -1 to 85 km/s, the molecular material successfully traces
the Local, Perseus, and Outer arms. In the TGQ, the Outer arm appears to be
more prominent than that in the second Galactic quadrant (SGQ), but the Perseus
arm is not as conspicuous as that in the SGQ. A total of 1,502 $^{12}$CO, 570
$^{13}$CO, and 53 C$^{18}$O molecular structures are identified, spanning over
$\sim2$ and $\sim6$ orders of magnitude in size and mass, respectively. Tight
mass-radius correlations and virial parameter-mass anticorrelations are
observable. Yet, it seems that no clear correlations between velocity
dispersion and effective radius can be found over the full dynamic range. The
vertical distribution of the MCs renders evident pictures of the Galactic warp
and flare.
