Answer:
Their sculptures and artifacts.
Explanation:
The Olmecs were extremely talented artists and sculptors: they produced many statues, masks, figurines (Yes, figurines were a thing back then), stelae (I know you're confused. A stela (the singular form of stelae) is an upright stone or column typically bearing a commemorative inscription or relief design, often serving as a gravestone.), thrones and more. However, they are best known for their colossal heads, 17 of which have been found at four different archaeological sites.
The first picture is an Olmec head, and the second is a stela.
Before the civil war cities were mainly industry based. Manufacturing goods was really the only thing that was done in cities.
Hernando de soto explored north america to find slave trade
The major obstacle to Islamic expansion in India was the presence of the Rajputs, a traditional patrilineal clan/warrior ruling class.