Abstract: Besides propagating in target space like a point particle, a
closed string is also able to wind around non-contractible circles. A
direct consequence thereof is T-duality. In the textbook example, it
identifies the closed string dynamics on a large and a small circle by
interchanging its winding and momentum modes. Patching a background by
such dualities clearly goes beyond the notion of conventional geometry.
However, there are extensive efforts to embed them into a framework
called string geometry. It provides access to a vast number of new
backgrounds with intriguing phenomenology, like e.g. the possibility to
obtain de Sitter vacua. Double Field Theory (DFT) is the most promising
approach to describe these backgrounds and their properties. But still,
it is closely related to the torus. I will present a theory based on
Closed String Field theory starting from a Wess-Zumino-Witten model
which goes beyond the torus. It plays an important role in clarifying
the recent confusion about different constraints in DFT. Furthermore it
allows to uplift a large class of new backgrounds to string theory.
These backgrounds are not T-dual to any geometric ones.