You will see the chamber and a wall with braille on it. The braille says 'Dig Here' You will soon gain access into the first sealed chamber. The wall will open (eventually) allowing you to catch Regice.
either left of lilycove, sandstorm bit or water near dewford
Go into the middle of the room and use FLY (like if you were going to fly to a different town) That should open up the braille door to the north, and you can fight Registeel!
Registeels' cave is on Route 120. Once you get near the lady who gives out berries, go up the stairs, through the long grass, and up another set of stairs. You should now be at Registeels' tomb.
south of fortree west of lilycove
There is no jirachi's cave.
To open the Cave of Origin in Pokémon Emerald, you must first go underwater to the Seafloor Cavern. There you must defeat Archie.
Beat the elite four the cave should open.
you go to aegis cave in registeels room and you go to kick butt.
there is no emerald cave but there are other caves in emerald.
that cave will open after beating the elite four near route 111
In order to open the Regis caves in Pokemon Emerald you first have to go to route 134 and dive into the cave. When you are in there use dig. The first Regi cave is located in the desert.
At the end of iron island there is a dark door(you have to have beaten the elite 4)