Dettifoss from the east - the largest waterfall (by volume) in Europe
It's 45 meters high and 100 meters wide, and so large that it's hard to view both dimensions - you can visit the falls from the east or west side (requires a long drive around) - the east side provides more of a view of the height and you can climb over rocks to get frighteningly close; the west side provides more of a view of the width.