The crystallography and microstructure of an antiferroelectric ceramic of approximate composition Pb0.97La0.02(Zr0.65Sn0.25Ti0.10)O3 have been examined. Transmission electron microscopy (TEM), x-ray, and neutron powder studies were carried out. The cell is metrically tetragonal with a c/a ratio of 0.993 when indexed to the parent cubic perovskite cell. The structure exhibits both a commensurate supercell, believed to be associated with oxygen octahedra distortions, and an incommensurate modulation. The different crystallographic variants of the tetragonal antiferroelectric phase gave rise to a hierarchy of domain structures. Charging of TEM specimens having an incomplete conductive coating caused domain migration.