This research direction explores the relation between quantum theory and spacetime physics. Exploring how quantum phenomena like Bell correlations, interference or superposition fit into spacetime and connect with gravity reveals fascinating and useful insights into both. Questions that we study include: what if the causal structure of spacetime is in a superposition? What happens if not only our particles, but also our reference frames are quantum systems? Can we use the structure of spacetime for novel quantum information-theoretic protocols or to derive parts of quantum theory? An ultimate goal of this research is also to obtain new insights into the old problem of quantum gravity. To this end, we pursue optomechanical experiments that aim to approach the quantum regime of gravity.