The Cold Storage (Japanese: 冷凍コンテナFreezing Container) is a building in Pokémon Black and White found inside of an area of warehouses to the south of Driftveil City. After defeating the Elite Four, Zinzolin of the Seven Sages can be found and arrested here.
Despite being a series of buildings, only one of the warehouses is large enough to enter. Inside this warehouse, some of the floors are frozen over, resulting in ice skating puzzles. There are Workers inside who will battle the player. In the back of the warehouse is a room where Zinzolin is both first and last encountered. Outside the warehouses, there are additional Workers that battle, as well as tall grass where Ice-type Pokémon can be encountered.
A colored background means that the Pokémon can be found in this location in the specified game. A white background with a colored letter means that the Pokémon cannot be found here.
In True Friends, Cheren revealed that he had later returned to the Cold Storage to learn more about Team Plasma's motives. At the Cold Storage, he had met Zinzolin, who had taken him to see how N awakened Zekrom. Upon seeing this, Cheren had chosen to start following Team Plasma's ideals.
Trivia
The in-game maps show the Cold Storage to be on the mainland of Unova. However, the facility is actually on an island.