Disclosed here is a composition comprising at least one high-density carbon-nanotube-based monolith, said monolith comprising carbon nanotubes crosslinked by nanoparticles and having a density of at least 0.2 g/cm3. Also provided is a method for making the composition comprising: preparing a reaction mixture comprising a suspension and at least one catalyst, said suspension is a carbon nanotube suspension; curing the reaction mixture to produce a wet gel; drying the wet gel to produce a dry gel, said drying step is substantially free of supercritical drying and freeze drying; and pyrolyzing the dry gel to produce the composition comprising a high-density carbon-nanotube-based monolith. Exceptional combinations of properties are achieved including high conductive and mechanical properties.