The bright nebula NGC 6334 extends nearly 0.4 square degrees across the sky and is located at a distance from the Sun of 1.61 kpc. This region contains some of the most active sites of massive star formation in our Galaxy. Discovered by their bright far-infrared emission associated with radio continuum peaks, these nuclei of activity are aligned along a dense molecular ridge that runs parallel to the Galactic Plane and stretches some 10 pc. It has a total mass of a few 10^5 msol. The physical characteristics of the active spots range widely, from well developed expanding HII regions to deeply embedded, still contracting, young objects detected only as millimeter sources, thus at their earliest observable stage of their evolution. The oldest optically visible round HII regions with central O-type stars are found in the southern parts. There is no clear spatial evolutionary correletion across the region. In this review we describe the observed characteristics of the giant molecular cloud complex and present detailed discussions on the individual centres of star formation.