Appears in collection : 2023 - T1A - WS1 - Quantum gravity and random geometry

Boundaries and corners of gravitational subsystems allow the construction of non-trivial Noether charges generating infinite-dimensional symmetries, which have been advocated as a new promising tool to understand quantum gravity. In this talk I will focus on classical properties of these symmetries, with the goals of explaining how they appear, how they provide a description of non-local observables, and how physical prescriptions are required in order to remove ambiguities in their construction.