The "Ice Prince" is the burial of a two-year-old boy from the early Middle Ages, dubbed like that because the burial was lifted en bloc - and to keep the layers and items and fragile textile remains from moving and getting damaged, it was frozen with liquid nitrogen first.
There's a podcast in German about this, where Tracy Niepold (my wonderful colleague and conspirator in so many textile ventures) is interviewed about her work on this exceptional find. You can listen to the episode here.