It's 1789, the 46-year reign (1740-86) of Frederick the Great ended only three years earlier and Berlin is one of the great capitals of the European Enlighentment. Not long after the end of the Thirty Years' War (1618-48) Berlin embarked in the construction of massive defensive system of walls and bastions in the star-shaped Renaissance manner. But by the time they were completed, the encircling fortications of Berlin had been rendered obsolete by advances in warfare technology and were completely gon in little more than a century.
If you look at a late 18th century map of Berlin you can still see the ghosts of the bastions, but the whole area of the walls is already taken by urban expansion. Cölln--one of the original areas that formed the core of the city--now appears as "Alt Cöln" to distinguish it from the "Neu Cöln" extension of the fabric over the southern portion of the city walls. In a similar fashion, Berlin proper has taken over the eastern area of the walls and Friedrichswerder over the western area of the walls.
By the end of the Thirty Year's war, the population of Berlin had dwindled to 6,000 inhabitants. After a century and a half of peace--via massive military buildups--and religious tolerance, it was reaching 150,000 inhabitants. And the map of the city reflects this growth, showing large new urbanized areas, extending along both margins of the Spree way beyond the original circle.