  In these notes we will review some approaches to 2+1 dimensional gravity and
the way it is coupled to point-particles. First we look into some exact static
and stationary solutions with and without cosmological constant. Next we study
the polygon approach invented by 't Hooft. The third section treats the
Chern-Simonons formulation of 2+1-gravity. In the last part we map the problem
of finding the gravitational field around point-particles to the
Riemann-Hilbert problem.
