Four new alkali uranyl molybdates have been prepared using a reactive flux technique. [Rb2Na2][(UO2)6(MoO4)8](H2O) (1) is monoclinic, I2/m, a = 14.3760(3), b = 13.9903(3), c = 23.0921(7)Å, β = 107.957(3)º, V = 4418.2(2)Å3; [Rb4Na2][(UO2)3(MoO4)4(Mo2O8)] (2) is triclinic, P-1, a = 7.5329(2), b = 7.9131(2), c = 13.3491(4)Å, α = 76.608(2), β = 83.667(2), γ = 82.048(2)º, V = 764.11(4)Å3; Rb10[(UO2)8O8(Mo5O20)] (3) is triclinic, P-1, a = 16.9823(4), b = 17.8883(4), c = 20.4050(4)Å, α = 108.619(2), β = 93.689(2), γ = 91.436(2)º, V = 5855.3(2)Å3; while [Cs7Rb7][(UO2)16O13(MoO5)5](H2O)5 (4) is monoclinic, C2, a = 33.8722(9), b = 33.8486(8), c = 7.4245(2)Å, β = 90.021(2)º, V = 8512.4(4)Å3. 1, 2, and 4 correspond to three novel architectures; the layers in 4 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.