It's just a place with lots of rooms, with a regular spawn of MVP. Different rooms have different MVPs. In some servers, it's common to have 4 different MVP arenas. Each arena has 8 maps. The further you go into the maps, the more frequent they spawn.
An example of MVPs that spawn in one of the MVP arenas on the server I play in are:
-Mistress
-Eddga
-Maya
-Moonlight Flower
Then there's a room with Lord of Death, Doppelganger, Osirirs and Drake. This may vary from server to server though.