There are 5 Tallneck Locations in Horizon Zero Dawn. You must climb and override all of them for the trophy “All Tallnecks Overridden” (Silver).
They are the biggest machines in the game and look similar to Brachiosaurus dinosaurs. They are walking in circles around a predefined area. There’s always a tall building, ramp or rock you can use to jump onto their neck. Then you must climb up to reach their head. Once on their head hold Triangle to override them.
This clears the fog from the respective map area so that you can see all map icons clearly.
After doing the first few story missions you will reach the area with the first Tallneck. After that you can get the remaining ones at any time you want. Some of them are in areas with high level enemies so be careful. Either rush past those enemies or wait until you are level 20 or higher.
#1 – 0:05
#2 – 1:20
#3 – 2:38
#4 – 3:40
#5 – 5:01