A stringy glimpse into the black hole horizon

We elaborate on the recent claim https://doi.org/10.1007/JHEP05(2017)094 that non-perturbative effects in ${\alpha }^{\prime }$, which are at the core of the FZZ duality, render the region just behind the horizon of the $SL(2,R{)}_k/U(1)$ black hole singular already at the classical level ($g_s=0$). We argue that the 2D classical$SL(2,R{)}_k/U(1)$ black hole could shed some light on quantum black holes in higher dimensions including large black holes in ${AdS}_5\times S^5$.