General view of old steam engine and other tools used on the Roça Sundy, near Santo Antonio, in Príncipe Island in São Tomé and Príncipe, on August 1, 2026. Located on Príncipe island, Roça Sundy is famous both for its cocoa production and the historical site where Arthur Eddington conducted observations proving Einstein's theory of general relativity. It is one of six roças recognized as UNESCO World Heritage sites. The Roças are historic agricultural plantations in São Tomé and Príncipe that were established by the Portuguese in the 19th and 20th centuries for coffee and cocoa production. Operating as self-sufficient, hierarchical complexes, they included processing factories, housing (sanzalas), hospitals, and railways. (Photo by Daniel BELOUMOU OLOMO / AFP via Getty Images)