White Pass Railroad snow plow train in Skagway, Alaska.
On September 19, 2011, this image had been posted in Flickr for over 18 months and had been viewed under 200 times. The next day it got caught in a viral viewing frenzy and shot up to more than 140,000 views in that 24 hour period (100 views per minute all day long).
This same thing happened twice to another image I call Merging Oceans.
And here is the same train 10 years later.