This achievement will unlock once
168 of the 240 riddler challenges have been solved
Press LB for XRay Vision Look for Trophies, Chronicles of Arkham, Interview Tapes, Chattering teeth.
When you enter an area a riddle will appear solve the riddle by focusing on an object and holding LB
Once you unlock the secrets of the map then the riddle locations appear on the map.
Here is a guide if you are struggling with any riddles.
http://www.gamesradar.com/batman-arkham-asylum-riddler-guide...