On string theory on AdS${}_3\times M_7$ in the tensionless limit

We review old and recent results on a special limit of string theory on AdS${}_3\times M_7$ with pure NS-NS fluxes: the limit in which the string length ${\mathrm{\ell }}_s=\sqrt{{\alpha }^{\mathrm{\prime }}}$ equals the AdS${}_3$ radius $R$. At this point of the moduli space, the theory exhibits special properties, which we discuss. Special attention is focused on features of correlation functions that are related to the non-compactness of the boundary CFT target space, and on how these features change when the point $k\equiv R^2\mathrm{/}{\alpha }^{\mathrm{\prime }}=1$ is approached. Also, we briefly review recent proposals for exact realizations of AdS/CFT correspondence at this special point. [] This is the transcript of the talk delivered by the author at the 8${}^{\text{th}}$ edition of the Quantum Gravity in the Southern Cone conference, held in Patagonia, December 16${}^{\text{th}}$ - 20${}^{\text{th}}$, 2019.