  We give an introduction to topological crystalline insulators, that is,
gapped ground states of quantum matter that are not adiabatically connected to
an atomic limit without breaking symmetries that include spatial
transformations, like mirror or rotational symmetries. To deduce the
topological properties, we use non-Abelian Wilson loops. We also discuss in
detail higher-order topological insulators with hinge and corner states, and in
particular present interacting bosonic models for the latter class of systems.
