According to some fans, the Shiganshina district within the walls in Attack on Titan is inspired by a real city in Europe.
Before being strong links with the Exploration Battalion in Attack on Titan, Eren, Armin, and Mikasa were originally from Shiganshina District, located south of the Maria Wall. This district and the others are surrounded by a system of three concentric walls.
These walls, called Maria Wall, Pink Wall and Sina Wall, allowed Humanity to be protected from the Titans until the fall of the Maria Wall and what followed in the story of Shingeki no Kyojin. You should know that the consequent structure is made of ramparts and this place with the medieval spirit of Attack on Titan would, according to some fans, be inspired by a real city in Europe.
Even though Hajime Isayama, the author of the manga Shingeki no Kyojin, has never confirmed the information, some fans believe that the German town of Nördlingen (Norlingue, in French) strongly resembles the Shiganshina district, under attack by the titans.
A German inspiration could indeed be plausible in view of the names with Germanic consonance given to some of the characters in Attack on Titan like Eren, Bertolt or even Reiner.
Nördlingen, medieval town
Old historic town of more than a thousand years located in Bavaria, Nördlingen has almost completely preserved its medieval appearance. It is one of the three cities of Germany, with Rothenburg (Rothenburg ob der Tauber, in German) and Dinkelsbühl, which still have complete ramparts and in good condition and through which one can access by five entrances.
Nördingen is dominated by the Daniel, a 90-meter-high Gothic-style bell tower of the former St. George’s Church. This steeple is reminiscent of the one in the manga and in the anime. The Gothic-style houses in Nördingen are very similar to the homes of residents of different districts, notably Shiganshina in Attack on Titan.
SNK fans visited Nördlingen: