This is the crowd before a riot in Vancouver

http://www.gigapixel.com/image/gigapan-canucks-g7.html

Put your cursor anywhere in the crowd and double-click several times and then use the scroll button in the centre of your mouse.
You may need to multiple times to increase the size of the face you are viewing.

You can zero in on one single face. The clarity is unbelievable. You can see - perfectly - the faces of every single individual
- and there were thousands!