At any point when you’re in Free Roam mode, even after the story is completed, you can get the “” achievement. Go to one end of the Gotham Pioneers Bridge, which connects the north and south sides of the city. Shoot the Grapnel Gun at the wires and use the Accelerator to keep yourself from touching the wires. Make your way to the other end of the bridge. If you touch the ground at any point before the end, it will not count and you will have to try again.