Lofn is a large young impact crater on Jupiter's Galilean satellite Callisto. It is superimposed on Adlinda multilayer structure obscuring about 30% of it. Another multi-ring structure—Heimdall is found to the south-west. (wikipedia entry)
A crater is a circular depression likely created by an impact event. On Callisto they are named after characters from myths and folktales of cultures of the Far North.
Image Source. Marker locations are approximate and may not always appear to align with image on map.