Master of the Mojave

 is an achievement in Fallout: New Vegas which is awarded for successfully discovering 125 locations.

This can easily be obtained by choosing the Explorer perk when you reach lvl 20 which shows all locations so simply go out and explore!

You can check how many locations you have discovered simply by looking it up in the 'Stats' tab on your Pip-Boy.

Bugs

 * Occasionally the achievement will not be unlocked when you have discovered the 125th location. This problem can usually be solved by reloading a save(needs confirmation)