'In urbem' translates to 'into the city' in English and is a phrase that showcases the use of the preposition 'in' with the accusative case, which indicates movement toward a place. This phrase is essential for understanding how certain prepositions interact with different cases in Latin. The preposition 'in' can govern either the accusative or ablative cases, depending on the context, making this phrase a practical example of that grammatical principle.