It has 99 floors,when you go to the 100th one you clear the dungeon.(you don't have to go to all of them if you recruit mew which you fight randomly between Floor 39 and 99 if you have the music box in you tool boxP.S.DON'T USE IT!)
The dungeon Buried Relic consists of 99 floors.
99
99
48 floors
A dungeon is a cave on pokemon mystery dungeon. It is a level with a series of floors/rooms and the object is to get to the end of the dungeon.
In buried relic on floors 15 25 and 35
30 floors
there is thirty floors
24 floors
there are 20 floors.
40
The Nightmare has 17 floors.