What is the fine-grained topic of the following text: Mardan, Pakistan -- Several articles recovered from Mardan, a tribal area in NWFP, like toilet trays, terracotta sculptures, coins etc indicate that the Greek, Roman, Iranian and Central Asian cultures deeply influenced the indigenous Gandhara art and culture in the region. Only return the topic.
Influence of Greek, Roman, Iranian and Central Asian cultures on Gandhara art and culture in Mardan, Pakistan