After you resurrect Africa and everyone in the Domicile in Crysta, you continue on to Tower 4.
Tower 4, 1F
Go inside. The Guardian is there. He sends out three Cadets. They are just normal enemies, so get rid of all three. When they are gone, the walls disappear to the left and right, allowing you to walk across the ropes. Be careful when walking to the ropes. It's easy to walk on the wrong spot and fall into the hole.
If you want a hint, and some experience, kill the Cadet in the southeast corner to find a wandering soul. It tells you to take bold chances.
If you explore the room, you discover that there is no way up. You have to take a bold chance. Fall into the hole anywhere in the room.
Tower 4, B1F
There are four holes in the floor here, and each one goes to a different area. Don't fall into the southeast hole. Any of the other holes are OK to fall into. If you did fall into the southeast hole, follow the path and go up a bunch of stairs until you go to a small room with a small hole. Fall into that hole to return to the first room and try again.
After you fall into the correct hole, make your way to the middle of the area, then go north. You will go up a path and reach a staircase that goes to a new area of the first floor.
Tower 4, 1F
Go south from the stairs. There is a treasure chest in the southwest of the room that contains 44 gems. In the southeast, there is Magirock. When you are done collecting those items, go back up to where you entered this room from the stairs, and go up the stairs on the left side. You'll go through a room with a Cadet, then you will go up another flight of stairs.
Tower 4, 3F
Go along the south path and go along the east side of the room, all the way south to the southern tightrope. Walk across the southern tightrope to reach a small ledge that has Magirock. Go west along the next rope, then go north to find two chests. The left one contains an M.Bulb and the right one contains a Life Potion. Use it right away to permanently increase your HP by 5.
Now fall into the hole in this room, and fall into the hole in the next room to reach the area that has four holes in it. Go to the southeast hole and fall in. Go north and up the stairs. Go up all of the stairs in the following rooms. You will reach a large room.
Go south, then west, then northwest to reach a small area with a chest. It contains Crystal Thread. Go south from there and cross the southernmost tightrope to reach the east side of the room. The southern rope is the easiest to cross, because the one above that has a platform in the middle with a spinning fireball on the edge. After you reach the east side of the room, go north to find Magirock. Go west along the uppermost rope to reach the resurrection door. Approach the door. The Guardian speaks, and you are sent to a dark room.
Dancing Huball Troupe
A line of Huballs moves around the room. You have to hit the golden Huball on the rear of the line to knock it off, making the line shorter. Keep knocking off the golden Huballs until you have killed the last quickly-moving Huball. After they are all gone, the "show" will end (it might take a while, so just stand around until it ends) and you are brought back to the tower. Go through the resurrection door. You will resurrect N. America and everyone in the Elder's house.
You can reach a secret area if you go south from Tower 4. However, you won't be able to do anything there until you have cleared all five towers.
Don't bother going to the fifth tower yet, because if you do, you will be immobilized and the Guardian will push you outside. Go back to the village and talk to Elle in the Weaver's house. She will ask for the Crystal Thread that you found in Tower 4. You automatically give it to her. If you talk to her again, she says to rest at the Elder's house and talk to her tomorrow.
Go into the bed in the Elder's house. You will wake up in the middle of the night. Go into the Weaver's house and check on Elle. Talk to her and she will ask if you are going to go far away. Answer however you wish. Then go back and rest in the Elder's house again. In the morning, visit Elle. She will give you Elle's Cape. Press SELECT to go into the box, then go into the Armor Room to equip the cape.
Now walk all the way back to Tower 5 and go inside.