Grassy Viaduct Cache Location is the probably the second you will encounter of a set of not-so-hidden cache locations in Final Fantasy VII Rebirth, a discovery mechanic which rewards you with 2-3 chests that you have to search the location for. This one is really easy but you need to watch out because it is really linked to the Thresher Waterwheel Cache Location.
To get to that one climb through waterwheel from the Thresher Waterwheel Cache Location into the brick wall and keep moving east along the wall.
Once you reach the biggest drop the quest will start, the rest is really easy to find, the first will be right behind and the other two will be along the wall going east, there are three in total.
