There are prisons (of sorts) on at least three islands.
Super Power Island
The prison is to the left of Main Street, across the bay. You can only go there when you have acquired your Superhero ID from the Masks and Capes store. You have to go to the costume store, then the Prison, before you go into the other areas where the super villains are.
Red Dragon Island
The Fortress is up the large steps in East Edo. You can climb to it to get a message from Jack and Annie, who are imprisoned there. You do not see the exterior when you are arrested yourself, because you can use the Amulet to escape back to the Tree House.
Ghost Story island
The prison is in the bay across from the Inn, to the right, while the Lighthouse is to the left. You should go to the Lighthouse first, leave the thermometer, and then go to the prison. When you return to the Inn, you will be called back to the Lighthouse again to see the Keeper.
you dont get in
The Poptropica warden and scientist are at the "County Prison".
figur the thing out
first, go to the prison.
You swim across the water to your right. There should be a prison.
Look for it when you use the lighthouse to look for it then use the boat to go to the prison
H and the wardens office
On the left of the island
Use the pickax to break out.
you have to go to the prison and climb up the wall.
go to prison h
Use the amulet to teleport yourself back to the tree house.
you get through security or you run your poptropica person for life