Rainbow Cloud (Japanese: にじのくもRainbow Cloud) is a secret seventh area above Pokémon Island. It is a large, rainbow-colored cloud above the island. Atop it, all the stars and constellations can be seen clearly.
In Pokémon Snap, after taking pictures of all six Pokémon signs, Professor Oak will realize the connection between them: They're all Pokémon which appear as constellations in the sky. He believes that this is a message on where the player should go next. The player will be sent up into this cloud to find the rarest Pokémon on the island.
This is a secret course... In that case, I should find the rarest Pokémon!
The whole course is a long encounter with Mew, and it is not unlikely that the whole course will be necessary to capture a good photograph of this Pokémon. Photos are distorted by Mew's bubble shield, resulting in nothing more than a big lens flare. So, it becomes necessary to knock this shield away, which is done in three parts.
Mew taunts the player by floating back and forth in front of the ZERO-ONE, making it vulnerable to be hit with a Pester Ball. When it is struck, it will fly away with its shield crackling with energy and evidently damaged. Doing this three times will cause the shield to dissipate.
Despite having lowered defenses, Mew is playful and keeps taunting the player, though this time in a more defensive manner. Mew will fly past in a different shield, now a moving target and only seen for a few seconds before disappearing behind the player. After the shield is hit three times with a Pester Ball, it will dissipate once more.
Mew appears from behind, chasing its shield. Hitting it with an item will cause Mew to spin in place and then look up, briefly giving a perfect picture pose before teleporting away, leaving behind only a few sparkles. If Mew is successfully hit, the step will be repeated to give the player an opportunity for more pictures. If the player does not hit Mew, it will reclaim its shield, though only one hit is required to knock the shield away.
Mew is such a rare Pokémon that any picture of it is a special shot with a large bonus. Taking a big enough picture of it can be worth 10,000 points.