  This thesis is devoted to the study of geometric aspects of black holes and
integrable structures in string theory. In the first part, symmetries of the
horizon and its bulk extension will be investigated. We investigate the horizon
conjecture beyond the supergravity approximation, by considering \alpha'
corrections of heterotic supergravity in perturbation theory, and show that
standard global techniques can no longer be applied. A sufficient condition to
establish the horizon conjecture will be identified. As a consequence of our
analysis, we find a no-go theorem for AdS2 backgrounds in heterotic theory. The
bulk extension of a prescribed near-horizon geometry will then be considered in
various theories. The horizon fields will be expanded at first order in the
radial coordinate. The moduli space of radial deformations will be proved to be
finite dimensional, by showing that the moduli must satisfy elliptic PDEs.
  In the second part, geometric aspects and spectral properties of integrable
anti-de Sitter backgrounds will be discussed. We formulate a Bethe ansatz in
AdS2 x S2 x T6 type IIB superstring, overcoming the problem of the lack of
pseudo-vacuum state affecting this background. In AdS3 x S3 x T4 type IIB
superstring, we show that the S-matrix is annihilated by the boost generator of
the q-deformed Poincar\'e superalgebra, and interpret this condition as a
parallel equation for the S-matrix with respect to a connection on a fibre
bundle. This hints that the algebraic problem associated with the scattering
process can be geometrically rewritten. This allows us to propose a Universal
S-matrix.
