Context :

Aims : We present a study of a large filamentary structure at z \sim 0.73 in the field of the COSMOS survey , the so-called COSMOS Wall .
This structure encompasses a comprehensive range of environments from a dense cluster and a number of galaxy groups to filaments , less dense regions , and adjacent voids .
It thus provides a valuable laboratory for the accurate mapping of environmental effects on galaxy evolution at a look-back time of \sim 6.5 Gyr , when the Universe was roughly half its present age .

Methods : We performed deep spectroscopic observations with VIMOS at VLT of a K-band selected sample of galaxies in this complex structure , building a sample of galaxies complete in galaxy stellar mass down to a lower limit of log ( { \cal M } _ { * } / { \cal M } _ { \odot } ) \sim 9.8 , which is significantly deeper than previously available data .
Thanks to its location within the COSMOS survey , each galaxy benefits from a wealth of ancillary information : HST-ACS data with I-band exposures down to I _ { AB } \sim 28 complemented by extensive multiwavelength ground- and space-based observations spanning the entire electromagnetic spectrum .

Results : In this paper we detail the survey strategy and weighting scheme adopted to account for the biases introduced by the photometric preselection of our targets .
We present our galaxy stellar mass and rest-frame magnitudes estimates together with a group catalog obtained with our new data and their member galaxies color/mass distribution .

Conclusions : Owing to to our new sample we can perform a detailed , high definition mapping of the complex COSMOS Wall structure .
The sharp environmental information , coupled with high quality spectroscopic information and rich ancillary data available in the COSMOS field , enables a detailed study of galaxy properties as a function of local environment in a redshift slice where environmental effects are important , and in a stellar mass range where mass and environment driven effects are both at work .