We show that negative (∇Φ) 2 , where Φ is the dilaton, leads to a rapid creation of folded strings. Consequently it appears that the interior of the SL(2, R) k /U (1) black hole is not empty, but is filled with folded strings.Motivated by [1] we speculated sometime ago [2] that a concrete way to express the challenge in having a non trivial structure at the horizon of a large Black Hole (BH) is to be able to write down an effective action that renders the horizon special. We claimed that such an effective action must involve a "horizon order parameter"; an operator whose expectation value indicates if we are inside or outside the BH. The horizon order parameter meant to be a trigger that modifies the physics inside the BH considerably compared to the standard physics outside the BH.Recently [3] it was argued that in the case of the 2D SL(2, R) k /U (1) BH [4-6] the horizon order parameter might take a particularly simple formwhere Φ is the dilaton. Outside the SL(2, R) k /U (1) BH the operator O is positive while inside the BH it is negative. Some indirect evidence from the exact reflection coefficient of [7] was provided that the SL(2, R) k /U (1) BH interior is not empty in classical string theory [8,3]. These papers, however, did not explain how come the SL(2, R) k /U (1) BH is not empty or what it is filled with. Moreover no relation with O was established. In particular it was not clear how the fact that O flips sign when crossing the horizon could possibly trigger non trivial effects inside the BH.1