In a BEC where the constituent atoms retain their spin degree of freedom, spin rotations combine with the condensate phase to yield a large manifold of physically distinguishable states. This leads to a set of topologically distinct phases with a rich phenomenology of topological defects such as vortices. Here I will give an introduction to topological defects in a spin-1 BEC and show how stable vortex structures can be understood from a hierarchy of characteristic length scales. Boundaries between topologically distinct regions are important for example in early-universe cosmology and superfluid He-3. I will propose a scheme for how such a topological interface could be created in a spinor BEC, and show examples of interface-crossing defect states, highlighting how ultracold atomic gases could be used as quantum emulators of for example cosmic topological defects.