Rick Riordan said this quote
“ The ruins stretch from the river to the base of that mountain over there, about half a kilometre.’ ‘How far is that in regular measurements?’ Percy asked. Frank rolled his eyes. ‘That is a regular measurement in Canada and the rest of the world. Only you Americans –’ ‘About five or six football fields,’ Hazel interceded, feeding Arion a big chunk of gold. Percy spread his hands. ‘That’s all you needed to say. ”