As its name suggests, the Piston Cave contains nothing but pistons that threaten to crush or push the Morph Ball off the edge into the lava.
Extreme precision and speed are required to evade the pistons, especially in the second half of the obstacle course, where the pistons will slam into walls or each other, ending Samus' life instantaneously. These make the maze incredibly difficult to complete, if not near-impossible. At the end of the cave there is a Shield Key, which unlocks the Artifact Shield of the Binary Subscripture that is also near the end.
Samus can skip the entire section of the Piston Cave by unmorphing at the Morph Ball tunnel in the Processor Core and performing "Missile Pushes" to blast herself into the tunnel that leads to the end of the cave.