Bell Tower Ho-Oh .

After obtaining the respective Bell and obtaining the Rainbow Wing, the player gets to encounter Ho-Oh on the roof of the Bell Tower.

In Pokémon HeartGold, the player obtains the Clear Bell and Rainbow Wing after clearing the Rocket Invasion at the Radio Tower,
and defeating the Kimono Girls in Ecruteak City. The Ho-Oh will be encountered at Level 45.

In Pokémon SoulSilver, the player obtains the Rainbow Wing from the Old Man in Pewter City.
The Ho-Oh will be encountered at Level 70.