It can be accessed after Black Tower is unlocked with the Unova Link's Key System. If a player of Black 2 clears Area 5 of the Black Tower, that player can send the Tower Key to White 2 players, granting them access to Black City, and consequently, the Black Tower.
It comprises ten randomly generated, progressively more complex areas, each with a number of Trainers. In each area, a randomly selected Trainer is the gate Trainer, who will unlock the door to the Boss Trainer's room when defeated. Defeating an area's Boss Trainer allows the player to challenge the next area. Each floor has a Doctor who will heal the player's Pokémon after being defeated in battle (meaning areas six and up all have multiple doctors), but only once. Some rooms will contain various puzzles allowing for players to use moves such as Flash to more easily maneuver the room. Unlike true battle facilities, the player will earn experience and money for winning battles, but will forfeit the money earned during the challenge if the player loses or retires. The player is also able to save the game and access all parts of the menu except for the Bag (except when giving a Pokémon an item to hold). Registered items and menus cannot be accessed via the Y menu. The C-Gear is, however, usable.
The normal Trainers in each area have a team of two randomly selected Pokémon from a personalized pool of Pokémon. The Boss Trainer of each area has three Pokémon, which are fixed for each battle. The normal Trainers' levels increase as the player progresses through the areas, beginning at level 47 and ending at level 77 in Normal Mode. The Boss Trainers' Pokémon have higher levels than those of other Trainers in the area. Boss Trainers' Pokémon always hold items, while normal Trainers' Pokémon only hold items on higher floors.
Starting from Area 6, the areas are separated into different floors, which the player has to explore in order to find the gate Trainer and/or the Boss Trainer. Each floor has its own rooms, Trainers, and Doctor.
Upon defeating the Boss Trainer of an area, the player is rewarded with one or two items within a selection, as presented below. As can be observed, players are rewarded much less for completing Areas 6-9 (and arguably 10) than they are for completing Areas 1-5, although the former have higher difficulty and require much more time to complete.
Normal Trainers use two randomly selected Pokémon from their personal pool. Each of these Pokémon has a randomly generated level (within the range for that floor) and gender (if the Pokémon's species has genders). Both Pokémon will match in level, but not necessarily in gender. Trainers give out 40 times the level of their Pokémon, except Rich Boys, who give 200 times the level of their Pokémon.
The Boss Trainers always use their same set of three Pokémon. Benga is the Boss Trainer of Area 10 in Black 2, and upon first visit in White 2. Players of White 2 will face Janna instead of Benga on subsequent visits. Each Boss Trainer has their Pokémon with three levels more and gives the player 600 more than the previous area's Boss Trainer.
Normal Trainers in Area 1 have Pokémon whose levels range from 47 to 50 in Normal Mode.