It’s an old tradition in Sweden to start a bonfire in the name of…probably some old pagan tradition. Apparently there are religious elements in it. I didn’t read much into it though. How I see this tradition is a nice way to gather people in a park and put on an entertaining show with witches dancing around the bonfire. There are concerts and no matter the weather(rainy day second year in a row) there are always families, youngsters and kids to participate. I recommend this event!