The headlight cloud in NGC 628: An extreme giant molecular cloud in a
  typical galaxy disk
  Cloud-scale surveys of molecular gas reveal the link between molecular clouds
properties and star formation (SF) across a range of galactic environments.
Cloud populations in galaxy disks are considered to be representative of the
`normal' SF. At high resolution, however, clouds with exceptional gas
properties and SF activity may also be observed in normal disk environments. In
this paper, we study the brightest cloud traced in CO emission in the disk of
NGC628.
  The cloud is spatially coincident with an extremely bright HII region. We
characterize its molecular gas properties and investigate how feedback and
large-scale processes influence the properties of the molecular gas.
  High resolution CO ALMA observations are used to characterize its mass and
dynamical state, which are compared to other clouds in NGC628. A LVG analysis
is used to constrain the beam-diluted density and temperature of the molecular
gas. We analyze the MUSE spectrum using Starburst99 to characterize the young
stellar population associated with the HII region. The cloud is massive
($1-2\times10^7$M$_{\odot}$), with a beam-diluted density of $n_{\rm
H_2}=5\times10^4$ cm$^{-3}$. It has a low virial parameter, suggesting that its
CO emission may be overluminous due to heating by the HII region. A young
($2-4$ Myr), massive $3\times10^{5}$ M$_{\odot}$ stellar population is
associated.
  We argue that the cloud is currently being destroyed by feedback from young
massive stars. Due to the cloud's large mass, this phase of the cloud's
evolution is long enough for the impact of feedback on the excitation of the
gas to be observed. Its high mass may be related to its location at a spiral
co-rotation radius, where gas experiences reduced galactic shear compared to
other regions of the disk, and receives a sustained inflow of gas that can
promote the cloud's mass growth.
