From GameWatcher: “If you plan on following Generation Zero’s string of main missions, you’re inevitably going to have to find a number of military bunkers. They’re all tied to the effort of discovering what happened to the missing population, but one thing they all have in common is that they’re not particularly easy to find. Thus, it’s not unusual to have trouble reaching the Generation Zero Vesslan Bunker Location.”
Source: N4G PC Generation Zero Vesslan Location – Where Is the Vesslan Bunker?