The Einstein Tower (German: Einsteinturm) is an astrophysical observatory in the Albert Einstein Science Park in Potsdam, Germany built by Erich Mendelsohn. It was built on the summit of the Potsdam Telegraphenberg to house a solar telescope designed by the astronomer Erwin Finlay Freundlich. The telescope supports experiments and observations to validate (or disprove) Albert Einstein’s relativity. The building was first conceived around 1917, built from 1919 to 1921 after a fund-raising drive, and became operational in 1924. Although Einstein never worked there, he supported the construction and operation of the telescope. The exterior was originally conceived in concrete, but due to construction difficulties with the complex design and shortages from the war, much of the building was actually realized in brick, covered with stucco. Because the material was changed during construction of the building, the designs were not updated to accommodate them. This caused many problems, such as cracking and dampness. Extensive repair work had to be done only five years after the initial construction, overseen by Mendelsohn himself. Since then numerous renovations have been done periodically. According to lore, Mendelsohn took Einstein on a long tour of the completed structure, waiting for some sign of approval. The design, while logical and perfectly sufficient to its purpose, stood out like an “ungainly spaceship” in the suburbs of Potsdam. Einstein said nothing until hours later, during a meeting with the building committee, when he whispered his one-word judgment: “Organic”. Mendelsohn himself said that he had designed it out of some unknown urge, letting it emerge from “the mystique around Einstein’s universe”.

(https://en.wikipedia.org/wiki/Einstein_Tower)