The Volcanic Asteroid is a common name given to the asteroid within Dimension X where the Technodrome is located during season 4, including the Vacation in Europe sideseason episodes, and early season 5 of the 1987–1996 animated series.
It has a breathable atmosphere, and consists of a lake in the central parts of one of the parts, and a mountain where the Technodrome is located when it's there. The mountain is volcanic, and errupts in the episode The Dimension X Story, burying the Technodrome even deeper in the nearby lava.
In Poor Little Rich Turtle, Krang tries to attach engines to the asteroid and use Buffy Shellhammer's rocket formula, to move the entire asteroid. It fails when Buffy Shellhammer tells Shredder the wrong formula.