European Union / 5 Euro, 2007

The world’s other dominant currency is the euro. Its pleasant banknote designs by Austrian Robert Kalina feature bridges, gates, and windows that vaguely resemble specific European landmarks but are in fact generic. The euro has one great advantage over America's currency system: rather than big purple numbers, the bills are distinguished by size. They range from 120 x 62 mm (€5) to 160 x 82 mm (€500). The bigger the bill, the more it’s worth. Simple.