This paper is aimed at giving an overview of the global properties of the rich cluster of galaxies ABCG 209 .
This is achieved by complementing the already available data with new medium resolution spectroscopy and NIR photometry which allow us to i ) analyse in detail the cluster dynamics , distinguishing among galaxies belonging to different substructures and deriving their individual velocity distributions , using a total sample of 148 galaxies in the cluster region , of which 134 belonging to the cluster ; ii ) derive the cluster NIR luminosity function ; iii ) study the Kormendy relation and the photometric plane of cluster early-type galaxies ( ETGs ) .
Finally we provide an extensive photometric ( optical and NIR ) and spectroscopic dataset for such a complex system to be used in further analyses investigating the nature , formation and evolution of rich clusters of galaxies .

The present study shows that the cluster is characterised by a very high value of the line-of-sight velocity dispersion : { \sigma _ { v } = 1268 ^ { +93 } _ { -84 } } km s ^ { -1 } , that results in a virial mass of M _ { vir } = 2.95 ^ { +0.80 } _ { -0.78 } \times 10 ^ { 15 } \mathrm { h ^ { -1 } _ { 70 } M _ { \odot } } within R _ { vir } = 3.42 h ^ { -1 } _ { 70 } Mpc .
The analysis of the velocity dispersion profile shows that such high value of \sigma _ { v } is already reached in the central cluster region .
There is evidence of three significant substructures , the primary one having a velocity dispersion of { \sigma _ { v } = 847 ^ { +52 } _ { -49 } } km s ^ { -1 } , which makes it consistent with mass estimates from weak lensing analyses .

This observational scenario confirms that ABCG 209 is presently undergoing strong dynamical evolution with the merging of two or more subclumps .
This interpretation is also supported by the detection of a radio halo ( Giovannini et al . 2006 ) suggesting that there is a recent or ongoing merging .

Cluster ETGs follow a Kormendy relation whose slope is consistent with previous studies both at optical and NIR wavelengths .
We investigate the origin of the intrinsic scatter of the photometric plane due to trends of stellar populations , using line indices as indicators of age , metallicity and \alpha /Fe enhancement .
We find that the chemical evolution of galaxies could be responsible for the intrinsic dispersion of the Photometric Plane .