From Bulbapedia, the community-driven Pokémon encyclopedia.
The clock tower (Japanese: 時計塔 clock tower) is an old landmark that stands in an unnamed, anime-exclusive town in Unova.
According to Nurse Joy, the clock tower is the oldest building in town. It was also home to Darmanitan and its two Darumaka friends. But suddenly, Darmanitan disappeared and the Darumaka started to steal food from people. Because the clock and bell did not work anymore, plans were made to demolish it.
Ash and his friends follow the two Darumaka to the clock tower. That's where they discovered the missing Darmanitan in Zen Mode. They also discovered that Darmanitan was using its Psychic powers to keep the clock tower's bell from crashing to the floor. The hook holding the bell broke and Darmanitan caught it before it fell but did not have the strength to hold its weight and went into Zen Mode. The Darumaka stole food to feed Darmanitan and ultimately save the tower from being destroyed.
Ash and Cilan used their Pokémon to repair the hook and reattached the bell to the ceiling, finally freeing Darmanitan and saving the tower. Because the bell started working again, it was decided that it would not be demolished but would be restored.
Pokémon seen in the clock tower