  The solar observatory Einstein Tower (Einsteinturm) at the Telegrafenberg in
Potsdam is both a landmark of modern architecture and an important place for
solar physics. Originally built for high-resolution spectroscopy and measuring
the gravitational redshift, research shifted over the years to understanding
the active Sun and its magnetic field. Nowadays, telescope and spectrographs
are used for research and development, i.e., testing instruments and in
particular polarization optics for advanced instrumentation deployed at major
European and international astronomical and solar telescopes. In addition, the
Einstein Tower is used for educating and training of the next generation
astrophysicists as well as for education and public outreach activities
directed at the general public. This article comments on the observatory's
unique architecture and the challenges of maintaining and conserving the
building. It describes in detail the characteristics of telescope,
spectrographs, and imagers; it portrays some of the research and development
activities.
