|The Archenhold Observatory, named in honor of Friedrich Simon Archenhold, is an observatory in Berlin-Treptow.
It was opened to the public on 1 May 1896 as the Treptow Observatory to coincide with the Berlin Industrial Show. Based on Archenhold's design it contained what was then the world's longest telescope, with a focal length of 21 meters. The Observatory was named after Archenhold at its 50th anniversary in 1946. The telescope was deactivated from 1958-1983 for repairs, and remains functional to this day.
The observatory is also noted as the location of Albert Einstein's first public lecture on the Theory of Relativity in Berlin.