Built in 1635 in the southern part of the Guén peninsula, the Fondo Tower was remodeled in the 17th and 19th centuries. It allowed for observations of the passages between Gaines and Porquerolles. It contained a barracks and a powder store. It is now owned by Port Cross National Park. Classified as a historical monument since 1989, it was restored in 1991, but due to security issues, the building is not open to the public, but its view can be enjoyed from the outside.