This chapter investigates the complex relation between iconic artifacts and their objects, using Harry Beck’s London Underground Diagram (LUD) as a key example. The LUD achieves optimal iconicity by strategically omitting superfluous geographic data, reframing the problem of navigating the urban network as a topological problem of diagrammatic connections. In doing that, the diagram of the subway grants semiotic objecthood to the subway. The generalization of this thesis has strong ontological implications: the mode of being of semiotic objects is that of problems.