Helps you know what the popular landmarks of a city are and how much time you would be spending at each city landmark.
Users typically click more than a couple of pictures when they visit a landmark.
Usually when they arrive at the landmark, sometime later and maybe when they leave.
The time a user is present at a landmark is estimated as the time difference between
his last and first clicked pictures at the landmark. This is averaged over several users who have taken pictures at the same landmark and the data is cleaned extensively to provide an informative experience.