What roles did many ancient cities, including Mathura, play in the subcontinent?

It was a Seat of commerce, culture, and political affairs.

A considerable number of the cities or the urban centes that emerged in various parts of India around 6th century BCE served as capitals of mahajanapadas, ancient kingdoms or republics. It is noteworthy that most major towns were strategically situated along communication routes. Some, like Pataliputra, flourished along riverine routes, while others, like Ujjayini, thrived along land routes. Coastal towns such as Puhar were essential starting points for sea routes.

Moreover, these vibrant cities, including Mathura, became bustling hubs of commerce, culture, and political affairs. Their significance as centers of trade and exchange, cultural exchanges, and seats of political power contributed to their growth and prominence during this period.