Top panel: redshift histogram of the 20 K-sample within the sky region targeted for observations. In red we highlight the subset of galaxies in the redshift range 0.72 ≤ z_spec ≤ 0.74, corresponding to the prominent peak of the COSMOS Wall structure. For comparison the orange histogram shows the photometric redshift distribution of the full 20 K-sample within the same sky region. The Wall volume redshift interval, 0.69 ≤ z ≤ 0.79 (indicated by two dashed lines), includes both the COSMOS Wall structure and two conspicuous lower density regions in the redshift ranges 0.71 ≤ z_spec ≤ 0.72 and 0.76 ≤ z_spec ≤ 0.77. Bottom panel: same as top panel but with superimposed (in orange) the histogram of the spectroscopic redshift distribution of the galaxies possessing a photometric redshift within the Wall volume: 0.69 ≤ z_phot ≤ 0.79.