To view unlocked locations (on XBOX) go to the map, and press the Y button to view from ORBIT, and then select the location and press LS (the left analog stick) to view progress
This achievement includes the following areas (with the amount of locations at each area in brackets):
-Meridian Outskirts (3)
-Meridian Metroplex (6)
-Lectro City (8)
-Skywell-27 (8)
-Atlas HQ (9)
-Neon Arterial (6)
-The Forgotten Basin (2)
-Cistern of slaughter (1) - accessible from Meridian Metroplex
AND not story relatededit: If anyone is still unsure what they are missing, the following website should help:
http://www.powerpyx.com/borderlands-3-promethea-all-named-lo...