Three-dimensional Einstein gravity has no local dynamical degree of
freedom. Yet, it is far from being trivial when the cosmological constant is negative. (i) It admits black hole solutions. (ii) It easily allows for consistently interacting and tractable higher-spin extensions.
(iii) It possesses remarkable asymptotic properties at infi�nity where
an infi�nite-dimensional symmetry algebra emerges. These features
make three-dimensional gravity a perfect "theoretical laboratory" in which to explore the conceptual issues related to (i), (ii) and (iii) in
a simpler context. The talk will not only discuss three-dimensional
gravity assuming no previous knowledge on the subject, but will also
provide access to recent work where new results on points (i), (ii)
and (iii) are developed.