A finite number of gravitating point particles in 2+1 dimensions may close the universe they are in. A formalism previously introduced by the author using tessellated Cauchy surfaces is applied to define a quantized version of this model. Special emphasis is put on unitarity and uniqueness of the evolution operator and on the physical interpretation of the model. As far as we know this is the first model whose quantum version automatically discretizes time. But also spacelike distances are discretized in a very special way.