How to Open the Prison Gate With a Hole in "Chrono Trigger"by Michael O. SmathersUpdated September 22, 2017
After the trial for allegedly kidnapping Marle in "Chrono Trigger," you are placed in prison pending execution in three days' time in game terms. Like most other areas of the game, Guardia prison has useful items for you to pick up. Exploration of the prison reveals a cell with two treasure chests, but you cannot reach them because the door is only open halfway. You have to reach the cell by another path. Remember to save your game before exploring the prison.
Go to the right from your prison cell and go up the first staircase. Two enemies will block your path; they are only vulnerable to attack when they turn their shields aside. After defeating them, go up the upper right staircase.
Cross the bridge into the next chamber. Hide in the alcoves when the guard looks at you and move toward him when his back is turned. Attack him from behind to deliver a one-hit kill without having to battle. You'll get a Mid Tonic for your Solid Snake impression.
Go north into a similar passageway leading to the left. A guard is blocking the staircase, so repeat the same tactic on him.
Go up the staircase, defeat the two shield enemies and take the upper left staircase.
Cross the bridge into the next cell block. Walk into the left hand cell and through the hole in the back wall.
Walk off the right side of the ledge, climb down and walk to the gap between the two ledges. Climb down this and walk in the door. You enter a similar prison cell with an open sewer grating/ladder. Collect the Shelter from the treasure chest and descend the ladder.
Collect 1,500 gold pieces and a Lode Sword from the two treasure chests.
You can walk between the shielded enemies on the staircases if you are properly aligned and don't try to run.