<p>Four new alkali uranyl molybdates have been prepared using a reactive flux technique. [Rb₂Na₂][(UO₂)₆(MoO₄)₈](H₂O) (<b>1</b>) is monoclinic, <i>I</i>2/<i>m</i>, <i>a</i> = 14.3760(3), <i>b</i> = 13.9903(3), <i>c</i> = 23.0921(7)Å, <i>β</i> = 107.957(3)º, <i>V</i> = 4418.2(2)ų; [Rb₄Na₂][(UO₂)₃(MoO₄)₄(Mo₂O₈)] (<b>2</b>) is triclinic, <i>P</i>-1, <i>a</i> = 7.5329(2), <i>b</i> = 7.9131(2), <i>c</i> = 13.3491(4)Å, <i>α</i> = 76.608(2), <i>β</i> = 83.667(2), <i>γ</i> = 82.048(2)º, <i>V</i> = 764.11(4)ų; Rb₁₀[(UO₂)₈O₈(Mo₅O₂₀)] (<b>3</b>) is triclinic, <i>P</i>-1, <i>a</i> = 16.9823(4), <i>b</i> = 17.8883(4), <i>c</i> = 20.4050(4)Å, <i>α</i> = 108.619(2), <i>β</i> = 93.689(2), <i>γ</i> = 91.436(2)º, <i>V</i> = 5855.3(2)ų; while [Cs₇Rb₇][(UO₂)₁₆O₁₃(MoO₅)₅](H₂O)₅ (<b>4</b>) is monoclinic, <i>C</i>2, <i>a</i> = 33.8722(9), <i>b</i> = 33.8486(8), <i>c</i> = 7.4245(2)Å, <i>β</i> = 90.021(2)º, <i>V</i> = 8512.4(4)ų. <b>1</b>, <b>2</b>, and <b>4</b> correspond to three novel architectures; the layers in <b>4</b> are characterized by a particularly complex topology. Topological analysis of known uranyl molybdates has been performed, which demonstrates that all their structures can be described as modular, i.e. constructed of some “basic” structural units of lower dimensionality.</p>