There are ten (10) Nenet monuments around the map. Find and inspect them all and the achievement should unlock.
LOCATIONS:
9088, 11440
6817, 10674
5871, 8968
4216, 7747
12133, 8935
9788, 7642
9070, 6781
11830, 5791
7710, 6300
6703, 6550
NOTE: There are reports of these achievements not unlocking correctly. The only way I know of to get them to unlock if they did not on your first try is to start a New Game. Unfortunately, this means you will lose all your progress.