Just completed the ahivement! Thanks for the sugestions, they helped me find one of the missing zones.
Also, here is one of the zones that contributes to the achivement and has not been mentioned:
http://wiki.guildwars2.com/wiki/Proxemics_Lab
It corresponds to a guild jumping puzzle.
Do you have to be inside the actual jumping puzzle to get the area. There is a text that says “Proxemics Lab” there on the map for me. Doesnt that mean that i have explored it?