Batman: Return to Arkham - Arkham Asylum

This achievement will unlock once 60 of the 240 riddler challenges have been solved

Once you unlock the secrets of the map then the riddles all appear on the map.

Make sure you batarang any teeth when you hear the chattering, also interview tapes are classed as riddles

Here is a guide if you are struggling with any riddles.

http://www.gamesradar.com/batman-arkham-asylum-riddler-guide...