Physics-minded visitors to Germany’s capital city of Berlin might be inclined to travel some 25 kilometers to the southwest, to the town of Potsdam. There, at the top of a hill, they can tour the Einstein Tower (Einsteinturm), and view a bust of Einstein in the lobby that was hidden by workers during World War II, to keep the Nazis from blotting out this tribute to the Jewish Einstein’s scientific legacy.

Designed and built by architect Eric Mendelsohn in 1921, the Einstein Tower went into operation in 1924. Yes, I said “operation” — it’s more than just a strikingly example of expressionist architecture. It’s also a bona fide research facility, where scientists study solar magnetic fields.

Among the central features of the Einstein Tower is its solar telescope, designed by astronomer Erwin Finlay-Freundlich and housed in the dome of the structure. (You can see the heliostat in the right of the photo, and a mirror on the left to reflect beams of light down the tower.)

Initially it was used to experimentally verify a prediction of general relativity: that there would be a small red shift in the spectral lines in the sun’s gravitational field.

But as it turned out, there were so many other solar effects taking place, that telltale shift was obscured. Scientists didn’t succeed in making the observation until the 1950s. Over time, the research focus shifted to studying solar magnetic fields, the primary focus of the work being done there today.

As for Einstein’s reaction when he finally toured the completed facility in the 1920s — well, it was surprisingly cryptic:

Legend has it that Mendelsohn took Einstein on a tour of the tower and waited patiently for the nod of approval from the world famous scientist. And waited. And waited. Much later, when Einstein met with the building committee, it is said he whispered a single word: “organic.” To this day, it is not known if this utterance was intended as an approval or opprobrium.

That Einstein. Always keeping ‘em guessing.