We present the results of a deep , wide-area , optical and near-IR survey of massive high-redshift galaxies . The Prime Focus Camera ( Suprime-Cam ) on the Subaru telescope was used to obtain BRIz ^ { \prime } imaging over 2 \times 940 arcmin ^ { 2 } fields , while JK _ { s } imaging was provided by the SOFI camera at the New Technology Telescope ( NTT ) for a subset of the area , partly from the ESO Imaging Survey ( EIS ) . In this paper , we report on the properties of K -band–selected galaxies , identified from a total area of \sim 920 arcmin ^ { 2 } to \hbox { $K _ { Vega } $ } = 19 , of which 320 arcmin ^ { 2 } are complete to \hbox { $K _ { Vega } $ } = 20 . The BzK selection technique was used to assemble complete samples of about 500 candidate massive star-forming galaxies ( sBzKs ) and about 160 candidate massive passively evolving galaxies ( pBzKs ) at 1.4 \lower 2.15 pt \hbox { $ \buildrel < \over { \sim } $ } z \lower 2.15 pt \hbox { $ % \buildrel < \over { \sim } $ } 2.5 ; and the ( R - K ) _ { Vega } > 5 color criterion was used to assemble a sample of about 850 extremely red objects ( EROs ) . We accurately measure surface densities of 1.20 \pm 0.05 arcmin ^ { -2 } and 0.38 \pm 0.03 arcmin ^ { -2 } for the sBzKs and the pBzKs , respectively . Both sBzKs and pBzKs are strongly clustered , at a level at least comparable to that of EROs , with pBzKs appearing more clustered than sBzKs . We estimate the reddening , star formation rates ( SFRs ) and stellar masses ( M _ { * } ) for the ensemble of sBzKs , confirming that to \hbox { $K _ { Vega } $ } \sim 20 typical ( median ) values are M _ { * } \sim 10 ^ { 11 } M _ { \odot } , SFR \sim 190 M _ { \odot } yr ^ { -1 } , and E ( B - V ) \sim 0.44 . A correlation is detected such that the most massive galaxies at z \sim 2 are also the most actively star-forming , an effect that can be seen as a manifestation of downsizing at early epochs . The space density of massive pBzKs at z \sim 1.4 - 2 that we derive is 20 % \pm 7 % that of similarly massive early-type galaxies at z \sim 0 . Adding this space density to that of our massive star forming class , sBzKs , in the same redshift range produces a closer comparison with the local early-type galaxy population , naturally implying that we are detecting star formation in a sizable fraction of massive galaxies at z > 1.4 , which has been quenched by the present day . Follow-up optical and near infrared spectroscopy is in progress at the ESO Very Large Telescope ( VLT ) and at the Subaru telescope , in order to elucidate more thoroughly the formation and evolution of massive galaxies .