Grand Koopa Canyon
From the Super Mario Wiki, the Mario encyclopedia
Located in Car Land, the only way to cross the Grand Koopa Canyon, aside from jumping over it, appears to be a bridge connecting both sides of the canyon. Located at the bottom of the Grand Koopa Canyon is a large river. Additionally, a large hole, created from when King-of-the-Road-Koopa crashed into one of the canyon's walls, is also located in the Grand Koopa Canyon.