The "resource" was knowledge and science. The reason Western Euroupe used to have vast empired was because of it's advanced science and military. It's economy used to (and still is) one of the major economic regions of the world, because of the Industrial Revolution (Originated in Great Britain) and other factors. They created the machinery that provided the base for economic and terratorial expansion. That, and having excellent universities and scientists (Issac Newton, Charles Darwin etc.) are key to keep fueling the economy, and growing to theone of the world's major economic region we know today.
Riddles were originally a form of oral literature, rather than written down, so think of how the riddle sounds when you say it. Try not to bog down your riddle with elaborate words or abstract concepts.
