Mt. Lavalava is a volcano on Lavalava Island in Paper Mario. As the main part of the chapter, it is where Mario finds the fifth Star Spirit, Misstar. It is also the home of the vile Lava Piranha. The Ultra Hammer is found here. Kolorado accompanies Mario through most of the volcano, but he's not interested in searching for a Star Spirit; rather, he just wants to follow Mario to get the treasure hidden in the volcano.
Names in other languages
When the Spiny Tromp is chasing Mario deeper in, it is a reference to the Indiana Jones movie series, when a boulder chases him down into an area.