Atlantis is the place that SpongeBob and his friends visit in Atlantis SquarePantis. As seen in the episode, the place is very high tech with things never seen before. The king of the city is Lord Royal Highness. it is also home to the World's Oldest Living Bubble, which Patrick accidentally popped. Atlantis has also been seen in Neptune's Spatula. Atlantis made its first main appearance in the episode Atlantis SquarePantis (Episode). Atlantis was usually the home for King Neptune, although Neptune wasn't king but Lord Royal Highness was.
In Mermaid Man and Barnacle Boy, SpongeBob talked about Atlantis where the city's food supply was running low, so Mermaid Man invented a 6-time ray gun that can increase anything's size multiplied 6 times but Man Ray steals the ray gun and shoots it at all the algae.
 City Areas
Armory Room: All weapons that they no longer use is locked shut and is unguarded. The weapons shoot only ice cream much to Plankton's dismay ("Ice cream? IT SHOOTS ICE CREAM!!!?**") Plankton's favorite room. Plankton's song So Many Weapons.
Art Room: Lots of great art projects are held in this room and visitors can go through all sorts of paintings they can think of. Squidward's favorite room. Squidward's song Pick up a Pencil.
Science Room: All inventions made by the city are held in this room. It has a machine that transports you inside the machine and so small that you can battle germs like a video game. Sandy's favorite room. Sandy's song The Germ Warrior.
Dining Room: Dinners and meetings are held here.
Tourist Area: The fake version of the oldest bubble for tourists to see is held here. Lord Royal Higness held the real one, when Patrick took a picture and popped it.
Atlantis Garden: outside the building that L.R.H. was in, there's a garden that SpongeBob and friends accidentally destroy. Squidward complained that it shouldn't have been destroyed.
The Poseidome: Where the Ultimate Cook Off is held. It also serves as a place to bid on who will win the competiton. Its name is also a parody of the Greek God Poseidon.
The castle: Where L.R.H. lives and where the door to the weapon room is locked with a combinational lock. Mr. Krabs finds out at this part that both cases of Squidward saying "The streets are made of Gold and the Lamps are made of diamonds" are not true.
Neptune's Palace: King Neptune's home where Gods live and where chosen fry cooks are chosen to cook for. It is a parody of a temple near Athens, and Thessalonica, Greece.
Bacteries area: It is featured as the second variant of 6th level in Atlantis SquarePantis.