Thwomp Volcano

Thwomp Volcano is a currently inactive volcano in the northwest corner of the Mushroom Kingdom. The Mario Bros. came here in pursuit of Bowser during the events of Mario & Luigi: Partners in Time. Young Elvin Gadd used to live here prior to its annual eruption. Thwomp Caverns can be accessed by using Mr. Thwomp as an elevator, and deep inside the caverns, Bowser and Baby Bowser are fought.

After the Hydrogush 4000 rendered it inactive, the Mario Bros. journeyed inside after being confronted by Mr. Thwomp and Mrs. Thwomp. Mrs. Thwomp becomes outraged that the volcano became inactive and her husband loses his confidence. After the battle with Mrs. Thwomp, Mr. Thwomp agreed to help the Mario Bros. get a lift inside.

Trivia

 * When Bowser and Baby Bowser get shot out of the volcano, they are going up. When Bowser is falling down, the scenery is still going up even though Bowser is falling.
 * Thwomp Volcano is the only area in the game where a species of Shroob is not a sub-boss or a main boss (Sub-Boss is Mrs. Thwomp and the main bosses are Bowser and Baby Bowser)