The ultimate goal in galaxy studies is to have a complete picture of galaxy formation and evolution across the history of the Universe. A robust determination of the abundance of massive (even quiescent) galaxies at high-redshift is essential to constrain current galaxy formation models. In this context, this work addresses the challenge of studying the build-up of massive galaxies adding a new population of optically faint (HST-dark) Balmer Break Galaxies (BBGs), which are bright at longer wavelengths (even in the sub-mm regime), to the general population of massive galaxies at z > 3. We study in detail the physical properties of the general population of known massive galaxies at z > 3 and we analyze the sample of BBGs by comparing them with a mass-limited (M > 10^10M��� and z > 3) sample and a color-selected (H ���[3.6] > 2.5) sample extracted from the CANDELS catalogs published for these fields. We have therefore detected a new population of previously unknown optically dark massive red galaxies and provide a more complete sample of the general population of massive galaxies at z > 3. This population of massive distant galaxies may represent the progenitors of most massive local galaxies. In the context of the current paradigm of galaxy formation, it is essential to constrain and confirm the number density of high redshift massive galaxies, which will provide crucial information to expand our understanding of galaxy evolution. The existence of this numerous population of massive galaxies at high redshifts represents a challenge for existing cosmological models and state-of-the-art simulations.