Cave Zone

A Cave to the Dark Path: The Cave Zone is an underground area of the unnamed island Popola inhabits. It is the fourth area the Straw Hat Pirates explore in One Piece: Unlimited Adventure.

Geography
The Cave Zone is subterranean region made up of caves and caverns. Its rock walls are dark grey, but some vegetation like shrubs and small trees can still grow up from them. Within the caves, pools of water and waterfalls can be found, as well as pits of magma. The area is dotted with stalactites and stalagmites, and cave ceiling heights vary from tight and low to tall and deep.

The Cave Zone connects to all other parts of the island and is the only zone to do so. It is also the only connector to the island's deepest, darkest area, the Abyss Zone, where the Evil Guardian was sealed away.

Enemies
At the beginning of the game, the following enemies appear:
 * Normal Marine
 * Bazooka Marine
 * Marine Leader
 * Saber Pirate
 * Knuckle Pirate
 * Sword Soldier
 * Knuckle Soldier
 * Mass Soldier

Arlong and Crocodile are the zone's bosses, and Paulie is the zone's secret boss.

One Piece: Unlimited Adventure
The Straw Hat Pirates entered the Cave Zone after Franky built a bridge in the Plain Zone to access its opening. They climbed down, and as Chopper snuck in slowly, Luffy and Franky jumped ahead with excitement. The explored the bowels of the cave, and Luffy used the orb near one of its walls, turning a large stone into a ball of energy. The ball dropped into the floor and opened a tunnel filled with light and platforms to the area's first seal. They found the Sword Soldier with Popola, and Franky tried to attack it. The monster dodged his Strong Hammer, but Popola jumped up from the ground to headbutt it. The Sword Soldier was crushed under some rubble.

Chopper realized that something was the matter with Popola, but the small creature jumped up from the ground and walked away from the crew toward the seal. Nami became frustrated and criticized Popola for taking on all of the responsibility to protect the island by himself. The orb then showed everyone memories of Popola protecting the island from pirates and visiting seals grave, and of Nami asking Luffy to save her from Arlong and the fishman telling her that he'd make her his mapmaker forever. The seal produced an apparition of Arlong, which the crew fought and defeated. The orb absorbed the seal's energy, and it showed them another memory of Luffy destroying Nami's mapmaking room in Arlong Park. Nami offered for the crew to help Popola, but the creature walked away alone.

The crew went deeper into the Cave Zone and came upon flowing magma. Luffy activated the orb, and a ball of water seeped out of the rock to cool off the area. The crew broke down the now cooled rock wall to reveal the next seal. As Luffy stood before it, Popola came up behind him. Popola jumped to attack him, but Luffy knocked the creature away. Popola continued trying to fight him, but Luffy kept deflecting him before grabbing him by his collar. Luffy confronted Popola about why he was so set on protected nothing, and the captain told Popola his dream before headbutting him. The orb showed the group a memory of Luffy fighting Crocodile underneath the Alabasta royal palace. The seal produced an apparition of Crocodile, who the crew fought and defeated. The orb absorbed the seal's energy, and the fourth seal on the entrance to the Abyss Zone shattered.

Luffy looked over to see Popola lying on the ground, and Robin tried to appeal to the creature to let them help him. Luffy demanded an answer, and the orb showed them a memory of Robin's declaration to want to live. Popola finally gave in and chose to accept their help. Luffy ordered his crew to defeat the Evil Guardian, and the crew, now accompanied by Popola, left the Cave Zone to return to camp.

After the crew destroyed the remaining seals, they descended through the Cave Zone to the Abyss Zone to fight the Evil Guardian. Upon defeating him, the Abyss and Cave Zones began to collapse. The crew ran through the Cave Zone, but when they were unable to leave safely, Luffy used Gomu Gomu no Gigant Pistol to break through the Cave Zone's ceiling and freely escape to the Plain Zone above.

Wildlife
Umbrella Frogs and Purple Poison Frogs can be caught along the partially submerged path next to the area's underwater ponds. Doze Evil Eye Butterflies, Lantern Fireflies, and Giant Devil Hand Moths can be found on the zone's flowers.

Lovely Angels, Cutie Piranhas, and Guidance Monkfish can be found in the Cave Zone's underwater ponds. Lava Flounder and Burning Dragons can be found in the area's magma pits.