In this talk I discuss the theory space of consistent theories describing one or more spin-2 fields (gravitons) from an effective field theory perspective. For a single graviton, this includes ghost-free massive gravity interactions and General Relativity, but also non-Einstein-Hilbert kinetic interactions and non-trivial couplings to matter. In particular I show in which sense General Relativity and ghost-free massive gravity are unique and that there is a very well defined set of other non-standard terms one can in principle add without destroying the validity of the theory.