The AdS/CFT duality maps supersymmetric heavy operators with conformal dimension of the order of the central charge to asymptotically AdS supergravity solutions. I'll show how, by studying the quadratic fluctuations around such backgrounds, it is possible to derive 4-point correlators of two light and two heavy states in the supergravity approximation. Then by using this input, I'll discuss how to reconstruct standard supergravity correlators between four (single particle) operators. I'll present some explicit examples in the AdS3 setup relevant for the duality with the D1-D5 CFT.