Sao Tome is the bigger island. It is not only the name of the island but also of the capital and of the highest mountain.
The cathedral and the fort of St. Sebastian are the main sights. Just 15 km from town you find the Casa de Repouso from where you get a great panoramic view over the island.
Great beaches are all around the island, but the best ones are found at prai das Pombas.