Nitrogen physical adsorption on carbon nanotubes bundles is studied with grand canonical ensemble Monte Carlo computer simulations in a wide temperature range. The results are compared with experimental data obtained in our laboratory and with that published in the literature. The characteristics of the sample employed in this work are also presented. The nanotubes are modeled by grouping them in bundles forming a hexagonal array. Local adsorption isotherms are calculated. The adsorption potential is analyzed, and the results are employed to interpret several distributions obtained from the simulations. The location of the expected adsorption sites is confirmed. The adsorbed phase within the tubes is characterized.