I know very little about the pre-colonial Americas, unfortunately, but I'm aware that a large number of pyramids and ziggurat-like-structures were constructed by various civilisations. Would these pyramids usually be situated in the midst of cities? Where was the manpower for their creation sourced - obviously, large numbers of skilled craftsmen would have been required alongside manual labourers. Finally, were these pyramids invariably religious in purpose, or would they serve other purposes such as palaces or forts?

I realise this is a sweeping generalisation of numerous different cultural groups and with no set time-period. Apologies for that - I honestly know so little about pre-colonial America that it's hard to give any specific details.