Haile Gebrselassie set a new marathon record a couple days ago: 2:04:26. That’s almost 13 miles an hour.
Update: Just to put this in perspective, the world’s best sprinters average about 23-24 miles an hour during their few seconds of exertion. Gebrselassie was going half as fast, but 400 times the distance, and 700 times the duration. It blows my mind.