The Ruins

From the Super Mario Wiki

Lucas explores The Ruins.

The Ruins is a stage found in the Subspace Emissary in the game Super Smash Bros. Brawl.

After a battle with Wario, Pokemon Trainer and Lucas venture inside The Ruins, where they're pitted against many enemies, falling spikes, moving platforms, and huge spikes. Halfway through, they meet face-to-face with a "trophy-ized" Ivysaur. Now having Squirtle and Ivysaur, the team continues through the Ruins, avoiding multi-man brawls, and even bigger threats. After making it to the end, they are face-to-face with a live Charizard, whom is soon defeated and captured by the Trainer. As they make there way through, they reach The Ruined Hall. After Galleom is defeated a second time inside the Hall, The Ruins is sucked into Subspace.

After the Emissary is beaten, the player can go back and enter a door not seen when exploring with the Trainer and Lucas, which will take the player to Lylat Cruise, where Wolf is fought. If he is defeated he is unlocked and joins your party.