The building resembles a Viking ship. Inside, it contains ancient artifacts, and other relics, such as formerly the Atlantian Amulet, which SpongeBob and Patrick completed to get a trip to the underwater city of Atlantis. Mr. Krabs took admission there (unofficially). Squidward was seen painting pictures that relate to Atlantis. It includes many artifacts, art, historical items, and many other things of ancient history.
Role in SpongeBob
It first appeared in Atlantis SquarePantis and SpongeBob's Atlantis SquarePantis. In both versions, Mr. Krabs tries to scam a customer out of money and Squidward puts the pieces of the Atlantean Amulet together, which summons a Atlantian Bus\Bus that will take Mr. Krabs, Squidward, Patrick, SpongeBob, Sandy, and Plankton to Atlantis.
In Atlantis SquarePantis, the customer being scammed is Miss Shell and SpongeBob find Squidward almost immediately after they enter. There is also a whole scene that explains what Atlantis is.
In SpongeBob's Atlantis SquarePantis is a Tourist. There is a whole level in the Bikini Bottom Museum.
Its second appearance, Are You Happy Now?, SpongeBob takes Squidward here to try to help Squidward to have a best memory. Squidward finds a statue of his in the museum. He is happy. Soon, Fiasco burns the statue. This makes Squidward sad.
The museum was bigger than it is now, but Patrick sat on a mine and part of it got destroyed.