" 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. "

― Rick Riordan , The Blood of Olympus (The Heroes of Olympus, #5)