Elizabethan dramatists often set their comedies in contemporary London. In contrast, Shakespeare chose distant eras and foreign cities as the milieu for his comedies. In A Midsummer Night's Dream, the city of Athens is barely shown as a city at all:
Shakespeare [..] tends to ruralise his comic cities: the Messina of Much Ado, the Padua of Taming of the Shrew, and the Athens of Midsummer Night's Dream lack almost all nitty-gritty traces of urban habitation but the name. (Paster 1985: 178)
In the play, the city of Athens is not realistically portrayed. Instead, it is a symbol of human society with its laws and regulations. The main function of this city, within the play, is its antithetical relationship to the free but wildly confused relationships of the forest - the human in contrast to the non-human.
In addition, the city can be seen as a symbol and realisation of civilisation and rationality.