The title compound (systematic name: 4,10-dinitro-2,6,8,12-tetraoxa-4,10-diazatetracyclo[5.5.0.0(3,11).0(5,9)]dodecane), C(6)H(6)N(4)O(8), exhibits the highest density among known N-nitramines, due to its close-packed crystal structure. It may be regarded as consisting of a distorted hexagonal close-packed lattice formed by the isowurtzitane cages, with the nitro groups occupying the free space between the cages.