The Chum Caverns are gorgeous caves. Plankton was able to lure customers in because of how beautiful the caves were. There is a stream, stalagmites, stalactites, and other wonders. Most of the customers were astonished at how cool it was, buying Plankton's 'inedible' food, just to bask in the caves glory. There is a gift shop; it is somewhere down near the tables.
The Chum Caverns are inhabited by strange orange indigenous species known as the Cave Dwellers. Plankton found them and, after brutally whipping them, made them his slaves, forcing them to serve customers. Later, at the end of the episode, the caverns get destroyed and the Krusty Krab falls into the cavern. Finally, one of these creatures is seen whipping Plankton at the check-out of the Krusty Krab. Later, Mr. Krabs makes the Cave Dwellers work the register.
Plankton and Karen found them in an attempt to get to the Krusty Krab. Plankton and Karen stayed because of the beautiful scenery the Chum Caverns had. In order to get to this underground paradise, you must get on a bucket-shaped elevator. (The elevator is shown below). This was used to get the Krusty Krab out of business by luring his customers here for the beautiful scenery, but this backfired later in "Chum Caverns."