The paper investigates the internal structure of cold dark matter (CDM) halos using high-resolution N-body simulations. As the mass and force resolution are increased, the density profiles of halos become steeper, asymptoting to a slope of approximately \(-4/3\) in the central regions. At the highest resolution, nearly 3 million particles are used within the virial radius \(R_{200}\), with force softening of about \(0.2\% R_{200}\). This resolution has allowed for the resolution of the overmerging problem, where over 1000 surviving dark halos orbit within a single cluster potential. The study provides unprecedented insights into the dynamics and structure of "halos within halos," allowing for the first time a comparison between dark matter distribution and observations of galaxies in clusters. The results show that the inner slope of density profiles can steepen to \(-1.4\), possibly due to the resolution resolving more halos collapsing at early epochs when the universe's mean density was higher. The distribution of halo orbits is nearly isotropic, with a median apocentric to pericentric distance ratio of 5:1. The mass bound to resolved dark matter halos is approximately 10% of the cluster mass, varying from 0% near the center to 20% at the virial radius. Overmerging in the central regions leads to an anti-biased distribution of substructure relative to the global mass distribution. Most halos within the cluster and in the cluster vicinity have density profiles well fit by NFW profiles, with some experiencing outer density profiles as steep as \(\rho(r) \propto r^{-4}\). Mergers between halos with mass ratios greater than 10:1 occur frequently in the cluster vicinity but are rare once within the virial radius.The paper investigates the internal structure of cold dark matter (CDM) halos using high-resolution N-body simulations. As the mass and force resolution are increased, the density profiles of halos become steeper, asymptoting to a slope of approximately \(-4/3\) in the central regions. At the highest resolution, nearly 3 million particles are used within the virial radius \(R_{200}\), with force softening of about \(0.2\% R_{200}\). This resolution has allowed for the resolution of the overmerging problem, where over 1000 surviving dark halos orbit within a single cluster potential. The study provides unprecedented insights into the dynamics and structure of "halos within halos," allowing for the first time a comparison between dark matter distribution and observations of galaxies in clusters. The results show that the inner slope of density profiles can steepen to \(-1.4\), possibly due to the resolution resolving more halos collapsing at early epochs when the universe's mean density was higher. The distribution of halo orbits is nearly isotropic, with a median apocentric to pericentric distance ratio of 5:1. The mass bound to resolved dark matter halos is approximately 10% of the cluster mass, varying from 0% near the center to 20% at the virial radius. Overmerging in the central regions leads to an anti-biased distribution of substructure relative to the global mass distribution. Most halos within the cluster and in the cluster vicinity have density profiles well fit by NFW profiles, with some experiencing outer density profiles as steep as \(\rho(r) \propto r^{-4}\). Mergers between halos with mass ratios greater than 10:1 occur frequently in the cluster vicinity but are rare once within the virial radius.