The Gritzy Caves, a place in Mario & Luigi: Partners in Time, is a series of caverns directly beneath the Koopaseum within the Gritzy Desert. Petey Piranha was found here during the course of the game.
The cavern has bluish stone and a sandy floor. Additionally, the walls are covered with vines and rock formations that resemble the heads of Piranha Plants. There are also many openings in the ceiling, allowing light in, however the cavern is mostly dim. Dark Boos, Elite Boom Guys, and Snifaros are enemies in this area. There are also Monty Moles, as well, two of which run an Item Shop called the Monty Mart.
Mario, Luigi, Baby Mario, and Baby Luigi enter the Gritzy Caves through the floor of the Koopaseum. A group of Shroobs carrying hammers surround them. They then strike the ground, making a hole which the Mario Bros. fall in. Soon afterwards, they encounter Kylie Koopa and a couple of Shroobs, only to see her fed to Petey Piranha who, earlier, had also eaten Princess Peach. But before the Mario Bros. can do anything, Petey Piranha burrowed away.
After traveling through the cavern, the Mario Bros. finally battle Petey Piranha. Once defeated, he explodes and both Kylie and a Cobalt Star Shard fly out of him, but Princess Peach does not. Kylie explains that when she was eaten she saw the princess, however, Petey spat her out right after swallowing Kylie. The Mario Bros. proceed a little further to reach a dead end where they encounter Princess Peach with a Shroob Mushroom on her face, which leads to them returning to the Mushroom Kingdom's present time.