  The advent of general relativity settled it once and for all that a theory of
spacetime is inextricably linked to the theory of gravity. From the point of
view of the gauge principle of Weyl and Yang-Mills-Utiyama, it became manifest
around the 1960s (Sciama--Kibble) that gravity is closely related to the
Poincare group acting in Minkowski space. The gauging of this external group
induces a Riemann-Cartan geometry on spacetime. If one generalizes the gauge
group of gravity, one finds still more involved spacetime geometries. If one
specializes it to the translation group, one finds a specific Riemann-Cartan
geometry with teleparallelism (Weitzenbock geometry).
