From Bulbapedia, the community-driven Pokémon encyclopedia.
Mistralton Tower (Japanese: フキヨセタワー Fukiyose Tower) is an anime-exclusive landmark in the Unova region. It is located along Route 7. A festival is held in its honor as well as a contest. Those who win the contest will have a chance to ring the bell at the top of the tower and make their potential wishes come true.
In Climbing the Tower of Success, Ash, Stephan, and Ricky race to the top of the tower holding Litwick-shaped candles to win the grand prize in the Wishing Bell Festival. The tower itself has an extremely long spiral staircase inside, and several Pokémon inside, such as Litwick and Frillish. It is unknown, however, whether these Pokémon are wild or belonging to a Trainer.
It is nearly identical to the Celestial Tower in design and location. However, it is not a cemetery for Pokémon as it is in the games.