Decay is a map for GTA V that allows players to explore the world in a different way. The gameplay of this mod is totally free. However, this mod could cause your FPS to drop, so be sure that your device is powerful enough to handle it.

In order to install it, you need to first download it. Once you download it, you need to open it via Map Editor and Scripthook V.

Load up the game and open Map Editor. Click on "Load map," hit xml, and then look for "DecayMap" in the file chooser. You can now go where the map is located.