Integrals of rational functions depending on parameters appear in many places in theoretical physics, for example as Feynman integrals in perturbative quantum field theory. Knowing the singularities of such integrals, as functions of the parameters, can be useful e.g. for bootstrap methods ('symbol letters'). I will review how the set of singularities can be obtained from the underlying geometry, and I will review recent joint work with Marko Berghoff (arXiv:2212.06661) that puts an order (hierarchy) on the set of singularities and thus provides constraints on iterated discontinuities. This provides an explanation of some of the so-called 'adjacency' or 'extended Steinmann' relations observed in the amplitude bootstrap. As an aside, I’ll illustrate a singularity of a Feynman integral that is not detected by solving the classical Landau equations.