|Arsubia or Baxteronia|
|First appearance||The Secret Guardians|
One day when Arthur, Binky, and Sue Ellen were out testing a model ship they lost the ship and discovered the place while chasing after the ship. After spending some time at the place, they decided to name the place. Binky wanted it to be called Binky's Butterfly Beach, as he saw many butterflies there. Arthur argued that the all found it and decided to call it Arsubi, as it was the first two letters of each of their names, but Sue Ellen thought Arsubia sounded better, so it was called that. After naming it, they swore on a rock to keep the place a secret. It also has a lake that connects to the river near the Tree House.
After a long few days keeping the secret, Buster found out that they discovered the place and joined them there. Although it used to be just for him and his dad, Buster let them all enjoy the place with him.
The place appears again in Speak Up, Francine!. Arthur, Buster, Muffy, and Francine walk by it briefly.