It depends on the accuracy you want to describe gravity. Gravity is equivalent to inertial forces in a limited region of space and time, over which the gravitational field can be assumed to be constant. Mathematically you can always find a reference frame, where at one point in space time you can describe locally everything as if there's no gravity and spacetime is described by Minkowski space. However, that's only true to the extent you don't look at higher accuracy for deviations, i.e., the socalled tidal forces, which occur on spacetime scales over which you cannot neglect to the given accuracy the inhomogeneity of the gravitational field. This manifests itself in a non-vanishing curvature of spacetime, i.e., you can approximate this curved spacetime only locally by a flat tangent space. That's analogous to the geometry on the earth. Only locally can you describe it by a flat Euclidean plane. As soon as you look over larger distances the curvature of the Earth becomes important for navigation.