mirage tower only appears in pokemon emerald.
In the desert and in mirage tower.
they are at the top of mirage tower the tower in the desert north of mauville city
go into the desert,and find the mirage tower
mirage tower or desert underpass
In the Mirage Tower nefore you get the Fossil
In mirage tower ( at desert near route 111)
Mirage tower will appear after talking to the fossil maniac he can be found just west from fallarbor town after talking to him go to the desert the tower will be there, you need the mach bike to go through the tower.
Ditto is found in mirage tower you can make the tower appear after talking to the fossil maniac.
Mirage Tower is in the desert around the enterance near Mauville. It only appears every once in awhile. I'm not sure how often though.
Mirage tower and underground tunnel in the fossil maniacs house.
In Pokémon Emerald, Mirage Tower will appear in the Desert that is to the North of Mauville City however it will only appear once you have spoken to the Ruin Maniac in Fallarbor Town. Once you head into the Mirage Tower, you will need to use the Bike that is the Mach Spike because of the various sensitive cracks in the floors. However once you have picked 1 of the Fossils then it (the Mirage Tower) will disappear and it will not return at all.