The Mannheim Squares
The unique chequered design of the City of Mannheim can be traced back to Prince Elector Friedrich IV of the Palatinate. Nearly 400 years ago, he ordered a fortified city to be constructed according to the latest standards at the confluence of the rivers Rhine and Neckar. The aim was for everybody to be able to easily orientate themselves in the streets of Mannheim.
Even today, when the city centre is characterised by letters and numbers instead of street names, the simplicity of this system is impressive: To the left of the historic baroque palace the quadrates start with the letter "A, ending with "K at the Neckar. To the right of the palace this continues with the letter "L up to the "U-quadrates on the banks of the river. However, there is one street name: the Breite Straße, which acts as a dividing line from the baroque palace to the Neckar. Starting from the Breite Straße, Mannheims quadrates are numbered outwards in both directions in ascending order, starting with number one. Each quadrate has its own "house numbers. They begin with number 1 at the respective quadrate street corner facing the palace, and from there go around the whole quadrate, anticlockwise in rows A to K, clockwise in rows L to U.
By the way, there are many stories about the "J quadrates but what you primarily need to know is that "I equals "J here, and vice versa!