Polymetallic complexes of Cu II represented the gateway to the field of molecular magnetism, beginning with studies of copper acetate 1 in the 1950s through to the development of magneto-structural correlations in hydroxide-and halide-bridged dimers in the 1970s and 80s. Later research revealed the presence of spin frustration in equilateral Cu II triangles and prompted detailed studies into the mechanisms of magnetic exchange. Indeed, high symmetry molecules are often ideal model complexes to examine geometric spinfrustration, and for larger nuclearity cages this can lead to some exotic behaviour including enhanced groundstate degeneracy, low-lying singlets, non-collinear ground states and unusual magnetisation plateaus/jumps. The synthesis of high symmetry molecules is however not trivial. One approach is to build small nuclearity, high symmetry complexes such as triangles or squares, since these are the building blocks of certain Archimedean and Platonic (or Keplerate) polyhedra, and assemble them into larger species often at high temperatures and pressures. An additional challenge comes in designing an organic ligand capable of stabilising such building blocks, and an excellent candidate is p-tert-butylthiacalix [4]arene (H4TC [4]A, Fig. ). This versatile molecule was first synthesised in 1997 and has since proved to be a highly successful platform for a breadth of supramolecular and coordination chemistry. In the latter area, the [S4O4] donor atom set typically leads to the formation of square [M4] building blocks that can self-assemble to form aesthetically pleasing molecular cages exhibiting a variety of nuclearities and topologies. This versatility is particularly appealing to chemists interested in constructing high nuclearity cages of paramagnetic metal ions with a view to developing magneto-structural correlations and/or uncovering novel magnetic phenomena. Surprisingly however, a search of the Cambridge Structural Database for TC [4]A-supported Cu II cages reveals just five hits: four [Cu4] squares and one [Cu13Na2] cluster. Herein, we outline the synthesis, structure and magnetic behaviour of a [Cu cage and a structurally related [Cu building block.