Bronze Key

The Bronze Mega Key is one of the first obtainable treasures in Pikmin: Connection of the Worlds. It looks like a giant, bronze version of the Key that was originally found in Pikmin 2. It is used to make the Garden and the Great Volcano explorable.

How to Obtain
If you didn't notice yet, there is a second passageway that leads away from the landing site. However, you won't be able to get far, as a paper bag blocks you. You'll be astounded by how much Pikmin are needed to crush it- 300! That's impossible- or is it? Go to the Frosty Depths, located at the end of the Frigid Fields subarea. Down at the 3rd floor, there are 3 Violet Candypop Buds! These can be used only when you have up to 30 Purple Pikmin. Now you can crush that paper bag that is preventing you from exploring further. After it is crushed, you are greeted by a welcome surprise- the Bronze Mega Key lay right in front of you! It weighs 100 Pikmin, but that doesn't matter. Just swarm all your Purple Pikmin and they'll carry it to the Ship in no time.

Use
The Bronze Mega Key is used for unlocking the Garden and the Great Volcano. On the world map, a cinematic will play. The giant key will start to glow, and it will fly up high, and it will shoot out a bright beam of light. The scene then switches to two giant domes. The light beam hits the domes and they shatter. The Garden and the Great Volcano are now explorable!