The Roman Baths, situated northeast of the Charlottenhof Palace in the Sanssouci Park in Potsdam, reflect the Italiensehnsucht of its creator Frederick William IV of Prussia. Various classical Roman and antique Italian styles were melded into an architectural ensemble, created between 1829 and 1840.
While still crown prince, Frederick William commissioned both Charlottenhof and the Roman Baths. Coming up with numerous ideas and drawing many actual drafts, the artistically inclined heir to the throne had considerable influence on the plans of the architect, Karl Friedrich Schinkel. Charged with managing the actual construction was one of Schinkel's students, Ludwig Persius.
Wikipedia https://en.wikipedia.org/wiki/Roman_Baths_(Potsdam)
Coordinates 52°23'46.81" N 13°1'42.016" E