The Einstein Tower is an icon of the modern age. It was built in 1920-22 by Erich Mendelsohn in a way that broke with all traditions. The Wüstenrot Stiftung has carried out the last two refurbishments of this significant monument. The Leibniz Institute for Astrophysics Potsdam (AIP) still operates the Einstein Tower in its original function: as a solar telescope.
Scroll through the history of science (above) and the history of architecture (below)!
Move the model and click on the buttons to learn all about the construction and function of the Einstein Tower!
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The Einstein Tower is a solar observatory operated by Leibniz Institute for Astrophysics Potsdam (AIP). The architect Erich Mendelsohn built the Einstein Tower between 1920 and 1922. The Wüstenrot Stiftung carried out the last two major restorations of the building between 1997 and 1999 and between 2021 and 2023, with care taken to preserve all the different historical layers. The digital exhibition »Einstein Tower revisited« invites you to immerse yourself in its history and the story of how it came into being, and gain an understanding of the building’s scientific programme. It also offers an insight into what is involved in preserving the tower as a monument.

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Mendelsohn's Sketches


“But when all’s said and done, there is something right about the first sketch. When it turns out to be correct, it is liberating, an unmistakable sign that the work is on its way to becoming art. This is the degree to which I submit to the power of the unconscious. The intellect assembles, but the intuition creates” (Erich Mendelsohn on his working method, 1928).

In 1912, after obtaining his diploma in architecture, Erich MendelsohnErich Mendelsohn (1887–1953) studied architecture at the Charlottenburg (Berlin) and Munich universities of applied sciences. He married Luise Maas in 1915. After returning from the First World War, he founded his own practice in Berlin – it became the best-known and most successful architecture office in Germany. In 1933 he emigrated to England, before moving to Jerusalem in 1939 and then to the USA in 1941. He built important works in all these countries. designed sets and costumes for the theatre. In the absence of clients to provide commissions, his built work was limited to “imaginary sketches”, which even then took a visionary delight in playing with new construction materials and the technical possibilities they offered.

Erich Mendelsohn
Erich Mendelsohn c.1925.

The outbreak of the First World War in 1914 did nothing to further the young architect’s career. Following the advice of friends, Mendelsohn volunteered for the Red Cross and received training as a medical orderly. His promotion to the rank of sergeant shortly before his marriage to Luise MaasLuise Mendelsohn, née Maas (1894–1980), studied cello in London, Leipzig, and Berlin. She met Erich Mendelsohn in 1910 and married him in 1915. Their daughter Marie Luise Esther was born in 1916. She abandoned her musical career and supported Erich when he started his own practice. Many of Erich’s jobs, including the commission for the Einstein Tower, can be traced back to the network Luise established. After the Mendelsohn family were forced out of Germany by the Nazis, Luise secured many new commissions for her husband. After Erich’s death, she organised his estate. in 1915 meant that he was liable to be deployed to the front. Luise used her contacts to have him transferred to the Pioneers in Spandau in December 1915, but in 1917 he was nonetheless ordered to the Russian front, which was fairly quiet at the time. Once there, he was able to keep working on his sketches, even though paper was in short supply. This explains why many of these drawings are small-format sketches. He used the army postal service to send them to his wife so that she could give her opinion and offer critical feedback.

“‘Freundlich’-esque, telluric and planetary”

At that time, Mendelsohn was already in contact with Erwin Finlay FreundlichErwin Finlay Freundlich (1885–1964) was an astrophysicist. In 1910 he became an assistant at the Berlin Observatory. He joined Einstein’s Kaiser Wilhelm Institute for Physics in 1918, becoming its first member of staff. He drew up plans for the Einstein Tower, which was to be the most powerful solar observatory in Europe. He was made director of the Einstein Tower in 1920. He was expelled by the Nazis and became a professor of astronomy in Istanbul. He was offered a professorship at the German University in Prague in 1936 and fled to Holland in 1939. He then took up a post at the University of St Andrews in Scotland, where he established an astronomy department, together with an observatory. He became Napier Professor of Astronomy in 1951., the astrophysicist who was seeking to prove the theory of relativity. At music evenings they held together, with Freundlich and Luise playing the cello, and in their exchange of letters, he told the Mendelsohns about his efforts to carry out empirical tests on Einstein’sAlbert Einstein (1879–1955) was one of the most important physicists in the history of science. He began developing the theory of relativity in 1905. In 1914 he joined the Prussian Academy of Sciences and in 1917 became director of the Kaiser Wilhelm Institute for Physics, which had been founded for him as a means to support his work. He won the Nobel Prize in 1921 (awarded in 1922). He spent periods teaching and conducting research in the USA. In 1932/33 he went to Princeton, never to return to Germany. He was clearly opposed to Nazi Germany and did not renew his ties with the country, even after 1945. He retired in 1946 and continued his work as professor emeritus at the Institute of Advanced Studies in Princeton. theory of relativity. Out of this came the first freehand sketches, which Erich sent to Luise on 24 June 1917 with the words: “After an hour’s nap, I was overcome by a sudden bout of drawing fever and produced a good many sketches, which may remain as they are in all their spontaneity or perhaps be brought to completion. That depends entirely on there being quiet time and on external factors.… They are for the most part ‘Freundlich’-esque, telluric and planetary.”

Skizzen zum Observatorium 1917
These sketches were produced before Freundlich provided his initial specifications, while Mendelsohn was on the Russian front during the First World War. Freundlich and Mendelsohn’s preliminary discussions about the Einstein Tower’s form and function were based on these sketches.

Das erste Briefing

On 2 July 1918, Freundlich wrote a letter to Mendelsohn, who was now stationed on the French front, providing a detailed description of the scientific functions required for the research facility: “Here are my thoughts on the matter. A 15-metre-high concrete tower is topped by a small dome with a diameter of between 1.5 and 2 metres. The tower is double-walled, i.e. its outer shell contains a completely insulated tube with a clear aperture of maybe 500 mm and a wall thickness of 500 mm. On top of the tube is a coelostatA celostat usually consists of two mirrors arranged in a way that a stationary telescope (e.g. a tower telescope) can be used to follow the motion of celestial bodies over the entire course of the day or night. (heliostat), which uses mirrors to project an image of the sun vertically downwards into an underground laboratory, with the slit, camera, and diffraction grating used for creating the spectrum horizontally mounted on a (separate) concrete base. The underground lab is some 15 metres long and only as high and as wide as is absolutely necessary, because it needs to be kept at a constant temperature. The lab is adjoined by several rooms, which are connected to it by little windows or double doors: 1) the room for the electric furnace, 2) the room for the electric arc lamps. They are both well ventilated and hooked up to high-voltage systems and air pumps. There is also a darkroom and a work room with an exit leading to the world above. At the foot of the tower there is just a small building with perhaps one or two rooms leading down to the laboratory. My sketch can, of course, only be understood in schematic terms.” He asked Mendelsohn for further sketches based on this programme and made simultaneous efforts to obtain money for the construction.

Einsteinturm, Ideenskizze, Observatorium und astrologisches Institut. Skizze des Aufrisses einer Seite
These sketches (sent from the French front in 1918) are a response to Freundlich’s initial “briefing”, which called for a workroom and laboratory spaces and stipulated a particular height for the tower telescope. Luise Mendelsohn promptly wrote to her husband on 12 July 1918 with her assessment of the design: “I prefer the project with the laboratory above ground: the upward graduation of the tower is staggered more effectively. Otherwise, the way it stands there makes such an abrupt impression.”

Sketching is thinking with a pen

The long prelude to the project during which Mendelsohn developed ideas for the tower telescope in direct communication with Freundlich without having received a commission for the work would pay off in the planning and construction phase, which was very short and intensive. The many adjustments that were necessary to marry the dynamic visions of the sketches with the technical requirements can also be seen in his further development of the sketches.

Skizze Mendelsohns für den Einsteinturm 1920
Variations on the theme, drawn in 1920 during the planning phase, which became increasingly more concrete. The sketches, which are also Mendelsohn’s colour studies, test out different design options for the front of the tower and various ways of structuring the building. “Absolute form also encompasses absolute ornament. It is light and the abstract of it is colour” (Mendelsohn in a letter to Freundlich dated 29/30 October 1917).
Entwurfsskizze Mendelsohns für den Einsteinturm aus dem Jahr 1920
In a letter to Luise dated 18 June 1920, Erich gave the following descriptions of the three enclosed sketches: “1. the earlier version; 2. the final version. You will recognise the last step by the omission of the corner pillars on each side of the entrance. This gives the idea of the ring its boldest expression as a sweeping curve of reinforced concrete at the point where it protrudes the most. I will use concrete for the entire superstructure and the side of the tower with the ring if it is at all possible. 3. A variant version of 2: The window ring is positioned in front of the wall surface. What do you think? We still have time.”
letzte Entwurfsskizze Mendelsohns für den Einsteinturm, 1920
This last and best-known draft sketch (prob. June 1920) can be seen as the essence of Mendelsohn’s approach to building from 1917 on: it takes into account both the scientific functions and the technical and financial feasibility.

Sketching would remain a constant element in Erich Mendelsohn’s life. He would typically embark on a new building project by doing a freehand sketch, which he would often work on while listening to the music of Johann Sebastian Bach. At the end of his life, he left behind an extremely varied body of work featuring buildings all over the world as well as a comprehensive legacy of drawings in an estate comprising 1,700 sheets of rough sketches.

Erich Mendelsohn beim Skizzieren in Amerika 1952, schräg von hinten, rauchend, die Asche der Zigarette ist lang, aber fällt nicht
Erich Mendelsohn sketching in America, smoking while he works (1952).