Grumble Volcano is a course in Mario Kart Wii. It reappears in Mario Kart 8 as a retro course. As it is titled, the track goes through the inside one of Koopa Kingdom volcanoes, and outside on a dirt track surrounded by shooting lava at night. As you go through the second and third laps, parts of the track, which can be identified by lines that cut around them, will start to rumble and shake and fall off into the lava. If you happen to be on them at this time, you will be pulled into the lava with them. Most of the track does not have crash barriers to keep you out of the lava.
Mario Kart Wii
After crossing the starting line, you'll jump off a ramp and head towards a tunnel. As you go in, you will be at the heart of the volcano where lava flows all around the fence-less track. You'll swirl and make a big turn right, and jump onto a round piece of track that sways side to side, and then enter another tunnel. In the middle, a barrier will separate the track. When it gives out, the left side will be higher than the right side. Either way you go, you will turn right after passing the barrier and then make a long left turn. At the end of the tunnel there will be another small barrier and then you'll jump off another ramp onto three more round pieces of track swaying side to side. Then, jump onto the next part of the track, where there is an elevated track with a ramp on the right, and a lower track on the left, but after a turn right, there will be a ramp to the left. At this part of the track there will be fire falling onto the track suddenly that will make you spin out if you run into it, along with small fireballs that jump out of pipes and bounce around causing the same effect that slows you down when you run into them. Then jump onto the last part of the track, where you can turn right, then make a left turn and head towards the finish line, or take the left route, turn right, and swerve towards the finish line. Both sides will find you jumping off another ramp and going straight towards the end of the track and making the loop again.
Mario Kart 8
Few changes appear to be in the track in Mario Kart 8, although a gliding ramp has been added after exiting the volcano.