The Witness: How to Solve the Garden’s Puzzles

One of the puzzles has two possible starts. In order to open the black panel, you’ll want to solve the one on the bottom first like this:

Then, return to the gate and solve the puzzle to open it:

After doing so, return to the puzzle with two solutions and do the top one, as you’ll need that later:

Now, go through the gate that has just been opened up. Head left and follow the wall until you find an open gate. This is the reason you needed to solve that puzzle with the two solutions fully.