The unique story of a tiny island paradise in the Americas that may belong to Germany has caused much interest over the years.
Highlighting the strong relations between the two communist nations in the 1970s, Castro made a promise during a state visit to East Berlin that he would donate one of Cuba's roughly 4,000 islands to the then German Democratic Republic (GDR).
The island, which was known as Cayo Blanco de Sur, was renamed after the German politician who had unsuccessfully run against Adolf Hitler in 1932 for the position of German president.
Ernst Thälmann, a Communist Party leader, was arrested by the Gestapo and forced to spend more than a decade in solitary confinement, before being shot dead on Hitler's orders in 1944.
Thousands of miles from freezing Berlin
The 15-kilometer (9-mile) long, 500-meter (1,640-foot) wide island still has many mostly untouched beaches, and is home to several endangered species of fish and coral.
One part of its coastline was also renamed, becoming the "Beach of the GDR."
A report by the German magazine "Spiegel" revealed how the island became a backdrop for many music videos by East German singer Frank Schöbel.
The island was often lauded by GDR state TV as marking close ties between Cuba and the GDR.
Tourism plan failed
Despite ambitious plans to turn the island into a tourist destination for East Germans, the project never took off due to financial problems facing the GDR at the time, reported "The Washington Post" following Castro's death on Friday night.
Following reunification, Germany has never laid claim to the island, and both Havana and Berlin insist the renaming was purely symbolic.
Today, the island remains uninhabited, apart from occasional organized tours.
A bust of Thälmann, which was erected in 1972, was knocked over when the island was struck by Hurricane Mitch in 1998.