Bowser's Lava Lake Keep is filled with lava and it ends with you chasing after Bowser in your 2nd fight against him.
The level starts in an area with many platforms, Podoboos, and Boomerang Bros., one of which drops a Boomerang Flower upon defeat. A nearby P Switch must be uncovered by kicking a Soccerbomb at the nearby wall hiding it. Hitting the switch results in a nearby bridge being lowered, which gives the player access to a Ka-thunk and Fire Bro-infested area, with the Checkpoint Flag near. After traversing a narrow pathway filled with Podoboos, the player has to defeat two Hammer Bros. in order to reveal a Warp Box that transports the player to a boss fight with Bowser in the Bowser Mobile.
The basic strategy to defeating Bowser is identical to the encounter in Bowser's Highway Showdown: the player must knock the Soccerbombs that he throws back at him by dashing into them. This time, however, the road is littered with hazards, including spike traps and gaps with lava geysers spurting out. Occasionally, the fight travels to a section of the road with a continuous gap in the middle, making it hard to hit the Soccerbombs. Bowser himself spits fire onto the road more often, and also occasionally throws Soccerbombs that are already close to detonation. Additionally, if the player managed to keep a Boomerang Flower, they can use it to deal small amounts of damage to the car.
Bowser is defeated when he is hit nine times, after which a Warp Box brings the player to the area with a red Sprixie Princess and the Goal Pole. However, when the player frees the last princess, Bowser appears and steals all seven once again, if the player use the two secret warps in World 1 and World 4, the Green and Orange Sprixie Princesses won't be seen.
- Green Star 1: Go through the level until you see it. Slide down the wall then do some wall jumps to prevent falling.
- Green Star 2: Just before you cross the bridge, climb up the wall to the left of it, and claim your Green Star prize.
- Green Star 3: Use the Boomerang Flower to obtain it, since it's in plain sight.
Once you blow up the wall with the P-Switch for the bridge, wall jump upwards until you obtain your Boomerang Mario stamp.