Im not writing an essay for you but I'll give an outline
P1: introduction. Introduce main points of how strength and intelligence contribute
P2: it took strength mentally and physically to build the city. Mental strength to persevere and physical strength to actually put it together
P3: it took intelligence because you would have needed to be smart to make good buildings. You'd also have to make the city safe for the people inside and keep attackers out.
P4: just the introduction in different, more concluding works