Reasoning About Space: The Modal Way M. Aiello, J. van Benthem, G. Bezhanishvili Abstract: We investigate the topological interpretation of modal logic in modern terms, using a new notion of bisimulation. Next, we look at modal logics with interesting topological content, presenting, amongst others, a new proof of McKinsey and Tarski's theorem on completeness of S4 with respect to the real line, and a completeness proof for the logic of finite unions of convex sets of reals. We conclude with a broader picture of extended modal languages of space, for which the main logical questions are still wide open. Keywords: spatial reasoning, modal logic, topological interpretation, topological bisimulations, chequered sets