Tungnaá is a river in the southern Highlands of Iceland that flows from Vatnajökull to the Sultartangalón reservoir where it meets the Þjórsá. It's been harnessed for hydroelectric power with stations at Vatnsfell, Sigalda, Hrauneyjafoss, and Sultartangi. So basically, it's a river doing its thing while also helping generate some electricity for Iceland. Cool, right?