The physics of a square lattice of pseudospin-half electrons in layered iridates has been shown to be particularly rich, giving rise to a novel playground for some of the most outstanding and challenging problems in condensed matter physics, such as metal-insulator transition and quantum magnetism. Significant interests have been focused on the analogy with high-Tc cuprates due to the appealing electronic and magnetic similarities with the CuO2 plane despite the much larger spin-orbit coupling (SOC) of Ir. However, unlike the large material family of cuprates, studies on the layered iridates have been limited to a few Ruddlesden-Popper (RP) compounds. This talk will discuss our recent work on overcoming this bottleneck by constructing different artificial variants of the two-dimensional (2D) lattice with heteroepitaxial growth of perovskite iridate. By tuning the layer dimension and the quantum confinement structure, our results show that the antiferromagnetic order and the magnetic interactions are highly sensitive to the lattice degrees of freedom. By leveraging with this structural control, we demonstrate a giant response of the 2D antiferromagnetic order to a sub-Tesla external field. This effect manifests a hidden spin rotational symmetry of the pseudospin-half lattice that was originally proposed for cuprates but never realized due to the small SOC of Cu, illustrating the power of atomic layering in exploring and revealing the intriguing SOC-driven emergent behavior beyond the cuprate phenomenology.