Its most notable feature is the powerful, nearly impenetrable airtight dome that surrounds it, letting no water seep in and allowing Sandy to survive without her special pressurized suit. On the inside of the dome, there is a picnic table, a hamster wheel, and a bird bath.
Despite being on the same street and one home next to SpongeBob's, the treedome is never seen directly next to the pineapple home, let alone anywhere near a street. Inside the dome, there is grass and sometimes flowers. There is a large oak tree in the center that provides Sandy with oxygen and acorns. The tree also serves as Sandy's house.
The treedome also has a mechanism that covers the dome with a layer of riveted sheet metal when Sandy wants her privacy. Other notable features are a boxing ring, weight lifting equipment and the "Arm Cruncher"—as seen in "MuscleBob BuffPants"--an exercise hamster wheel, clothesline for hanging Sandy's suit and clothing to dry - as seen in "Prehibernation Week" - a garage for Sandy's jeep-like boat mobile—as seen in "To Save a Squirrel"--an escape pod to Texas, a picnic bench and table, a miniature submarine for emergencies—first seen in "Squidtastic Voyage" - and a rocket for the Moon - as seen in "Sandy's Rocket."
In the winter, there is snow that covers the whole ground and sometimes there are no leaves on the tree. It is also very cold. This is seen in the episodes "Bubble Buddy" and "Survival of the Idiots."
Inside the tree
Inside the oak tree, there is a bedroom with a wooden bed, a rocking chair, and nightstands made out of sticks from the tree. Also inside her tree is her house telephone, which is made from a small wooden log, two acorns used as mouth and ear pieces, and green vine serving as a telephone cord. In "A Flea in Her Dome," it is shown that there is an automated trapdoor in her room which is stationed over a metal slide that leads outside the tree. There is a large living room with rugs, a television, and wicker sofas and chairs.
There is a bathroom with a shower stall. It also has a tree stump for Sandy's spacesuit, and a hook to hang her fur pelt when she's not wearing it. There is also a sink and medicine cabinet. Its lock is on the outside in the episodes "Someone's in the Kitchen with Sandy," "Survival of the Idiots," "Pranks a Lot," "A Flea in Her Dome," and "MuscleBob BuffPants."
The treedome has seen many visitors and inhabitants. Only some of them are below, which are separated into two groups; land creatures and sea creatures. Due to there being no water and only air in the treedome, land creatures can live in there, while sea creatures must wear water helmets on their heads so they don't dry out or get dehydrated. This is a parody of Sandy's required air helmet when out in the ocean.
Sandy Cheeks is the primary resident of the treedome. She uses it as a home to survive underwater. She also uses it to create inventions for her chimp bosses. She practices karate with SpongeBob here and takes care of her pets.
Sandy is revealed to own many pets: In the episode "Wormy," Sandy has many fellow land animals as pets to keep her company, with the most notable being Wormy.
Professor Percy: One of Sandy's chimp bosses. Like his fellow chimps, he premiered in the episode "Chimps Ahoy;" when he came to inspect Sandy's inventions to judge if she could stay longer.
Dr. Marmalade: One of Sandy's chimp bosses. Like his fellow chimps, he premiered in the episode "Chimps Ahoy," to inspect Sandy's inventions to judge if she could stay longer.
Lord Reginald: One of Sandy's chimp bosses. Like his fellow chimps, he premiered in the episode "Chimps Ahoy," when he came to inspect Sandy's inventions to judge if she could stay longer.
SpongeBob SquarePants: A good friend of Sandy and Patrick. Likes to come to play with Sandy, practice karate with her, or sometimes even help Sandy with her inventions. He usually causes much less chaos than Patrick in comparison.
Patrick Star: A good friend of both SpongeBob and Sandy. He usually comes with SpongeBob to play with Sandy and causes havoc to the treedome and Sandy's inventions.
Squidward Tentacles: A partial friend to Sandy, who does not spend a lot of time with her. He gets help from Sandy, SpongeBob, and Patrick in the episode "Squidtastic Voyage" to get the reed of his clarinet removed from his throat.
Sheldon J. Plankton: In the episode "Someone's in the Kitchen with Sandy," he is accidentally brought in with Sandy's suit. He steals Sandy's fur pelt and helmet while she was in the shower. SpongeBob also brings Plankton is a small glass of water into Sandy's treedome in The SpongeBob Movie: Sponge Out of Water.
Karen Plankton: She visits the treedome at the end of "Girls' Night Out," when Sandy invites her and Mrs. Puff inside her amoeba experiment. Karen also mentions the treedome in "Salsa Imbecilicus."
Bikini Bottomites: All of the other inhabitants of Bikini Bottom: At the end of the episode "A Flea in Her Dome," they are sucked into the treedome when Sandy opens the treedome to flood it with water to drown the invading fleas inside.