Suppose we are in a Minkowskian space, away from all the source of gravity, and observe an accelerated frame from this frame. Acoording to Equivalence principle, we can consider the accelerated frame to be at rest and assume we have gravity in the accelerated frame. Thus, observer in the accelerated frame will observe that his space-time is curved. What will this observer in the accelerated frame attribute this space-time curvature to? In other words, since the curvature has to be created by a mass, what is causing the curvature in his space?