The following classification levels have been legislated by the guys at sewerfresh.com. Please read this document carefully as it pertains to all those who wish to use the popular title Urban Explorer (and of course the detestable term UEr/UEer) in both public and private correspondence. If you resemble the person pictured below it absolutely does apply to you, tard.

Comments
looks like I need to spend some time in paris before I can move up to level 4, might have to see if I can RPL my way past it ;)
Don't forget the "proven leg stamina to dodge trains in a live underground system"