Fast radio burst are bright, millisecond-duration flashes of extragalactic origin, so far only observed at centimeter- to meter-wavelengths. The vast majority of the roughly 150 published FRBs have only ever been seen once, roughly 20 are known to burst repeatedly, but do so in an unpredictable way. Key ingredients in understanding the source and physical origin of the emission are the environments the bursts are generated in and their spectro-polarimetric properties. In this talk I will summarize the field and discuss the efforts that we conduct at Onsala Space Observatory. Besides running a VLBI-campaign to precisely localise FRBs, we also perform multi-telescope, multi-band observations in collaboration with Westerbork (NL) and Torun (Poland). In 2020 we detected FRB-like bursts from a Galactic magnetar and, most recently, we precisely localised two FRBs.