Here's a short video of the Eiffel Tower flashing on the hour.  I was taking the photo below when the Eiffel Tower started flashing.  It actually surprised me even though I had been in the tower while it was flashing in the previous hour.  I was inside on the second level getting a snack and studying a map trying to figure out where we'd go next when I noticed some flashing lights.  It never dawned on me that the entire Eiffel Tower was flashing until I saw it again from below.

Here's a picture of the Eiffel Tower lit but not flashing.
Here's the tower flashing.
Video and photos all capture with the iPhone 3GS.