Rings of ions trapped in radiofrequency (rf) multipole traps are extremely interesting candidates for a number of applications concerning high-resolution spectroscopy, in particular due to their (symmetry) properties. This lecture reviews the characteristics of these structures, the required experimental conditions, and proposes applications for these novel ensembles. It will be shown, that rings of ten or twenty ions can reach very similar high-resolution performances as single-ion systems, with a dedicated example in frequency metrology. Numerical simulations of ion dynamics and the experimental realisation of a multipole system give insight into opportunities and limits of rings of trapped ions.