Tomos Island (also commonly called the Treasure Island by Nobita) is a now-abandoned island that appears in the 1998 movie Doraemon: Nobita's Great Adventure in the South Seas. Discovered in the sixteenth century, it is situated in the Caribbean sea, off the coast of Cuba.
It is a large island with an extinct volcanic formation at its center, inside which sits the abandoned control tower of Mr. Cash, an illegal animal-trader. The rock is surrounded by dense forests and the beaches are abundant in coral reefs. The island has numerous caves built by Mr. Cash and his company, primarily to discourage outsiders from exposing the deeds of the company. It has a vibrant ecosystem consisting of diverse species of plants an animals (mostly created by Mr. Cash), geographical features including deep canyons and waterfalls.
Dr. Cash, a convicted criminal from the twenty-second century, travelled back to the seventeenth century to produce mixed animals with the help of his assistant and scientist Dr. Clone, and planned to sell them back to the future. A laboratory and secret base was built inside the volcanic formation and underground. A theory of a treasure was spread around so that medieval pirates would be attracted towards the island and could be used as slaves for the company. A protective screen was set up around the island, which would prevent the Time Patrol from detecting the island. Plants and animals around the island were genetically modified to pose as a threat to any outsider who tries to search for the treasure. Spy cameras were set up at various places around the island to detect activity.
Genetically modified animals were released around the island, along with a gigantic sea-monster that roamed the surroundings.
With the coming of the gang and the pirates, Cash's animal-trade plan was abolished. The base was destroyed during the process and as the protective screen had been removed, Time Patrol detected the island and arrested the workers of the company. The modified animals were taken back to the future, but the monster was left behind to become a folklore in the future.
The laboratory, built by Cash's company in the seventeenth century, also acted as a hideout for them. It consisted of an experiment laboratory, a few bedrooms for the crew, a prison, an animal cage-facility and a control tower. It was built inside the rocks of the volcanic structure. The factory used hydro-electricity for the power it needed. The control tower has a chamber for Mr. Cash and all the controls for the laboratory, including monitors for the spy cameras. At the top floor of the tower is a direct switch line board which has the buttons for the animal cage-facility. It has a vent at the top, through which Doraemon and Nobita fell down, knocking Cash out while he was using these.