Plateau's problem asks whether there exists a minimal surface with a given boundary in Euclidean space. In this course, we will study related problems in broader classes of spaces and ask what the asymptotics of filling problems tell us about the geometry of surfaces in groups and spaces. What do minimal and nearly minimal surfaces look like in different spaces, and how is the geometry of surfaces related to the geometry of the ambient space? Our main examples will arise from geometric group theory, including nilpotent groups and symmetric spaces.