  The tight correlation between turbulence and luminosity in Giant HII Regions
is not well understood. While the luminosity is due to the UV radiation from
the massive stars in the ionizing clusters, it is not clear what powers the
turbulence. Observations of the two prototypical Giant HII Regions in the local
Universe, 30 Doradus and NGC604, show that part of the kinetic energy of the
nebular gas comes from the combined stellar winds of the most massive stars -
the cluster winds, but not all. We present a study of the kinematics of 30
Doradus based on archival VLT FLAMES/GIRAFFE data and new high resolution
observations with HARPS. We find that the nebular structure and kinematics are
shaped by a hot cluster wind and not by the stellar winds of individual stars.
The cluster wind powers most of the turbulence of the nebular gas, with a small
but significant contribution from the combined gravitational potential of stars
and gas. We estimate the total mass of 30 Doradus and we argue that the region
does not contain significant amounts of neutral (HI) gas, and that the giant
molecular cloud 30Dor-10 that is close to the center of the nebula in
projection is in fact an inflating cloud tens of parsecs away from R136, the
core of the ionizing cluster. We rule out a Kolmogorov-like turbulent kinetic
energy cascade as the source of supersonic turbulence in Giant HII Regions.
