We present a summary of the results from the kinematic study of the extended gas in a sample of 10 high redshift radio galaxies (z~2.5) based on high S/N Keck spectroscopy. We find that, in addition to the typical high surface brightness kinematically perturbed regions, giant low surface brightness quiescent haloes are detected in all objects. We suggest that we have resolved kinematically the emission from ambient non-shocked gas (the quiescent haloes) and the emission from (jet induced) shocked gas. The haloes often extend for more than 100 kpc and sometimes beyond the radio structures. The quasar continuum is the dominant source for the ionization of this very extended gas. The kinematic properties are consistent with gravitational motions and are similar to those seen in low redshift radio galaxies. They are enriched with heavy elements at tens of kpc from the active nucleus. The discovery of the giant quiescent haloes in all objects suggests that they are a common ingredient of high redshift radio galaxies. Although the nature of the haloes-be they disks, spherical envelopes or cooling flow nebulae-is not clear, they are giant gaseous reservoirs within which the radio galaxy is embedded. The giant elliptical galaxy might have grown (or still be growing) from the giant halo.