"jeder" (every, each) is an article word which takes the same endings as the definite article.

It occurs only in the singular.

After the preposition "in" the dative case is used to indicate location (i.e. you can ask "where?")

-> Where can you see the graffiti? In the city.

[After the preposition "in"  the accusative case is used to indicate movement to a place (i.e. you can ask “where to?”), e.g. Die Busse fahren in jede City.]