Today large parts of the ancient city of Pergamon lie beneath the current city of Bergama. Thriving on top of the ancient remains, the site consists of numerous historical layers ranging from the Roman period up to today. Thanks to its rich history, the city has been inscribed on the World Heritage List of UNESCO in 2014 with the title “Pergamon and its Multi-Layered Cultural Landscape.” In 2013 an octagonal structure was discovered in one of these multi-layered spots where the Roman imperial expansion of the city and the 19thcentury residential settlement meet. Hints in archival documents revealed that this is actually a “rediscovery,” which highlights the importance of archival materials for current research projects in ancient cities like Pergamon that has a fairly long history of research. This article mainly examines the blanks and hints in the research history of the Octagon in three excavation periods. After summarizing the most recent discovery of the ancient structure, it addresses access issues as well as its state of preservation and the research methodology shaped in accordance with current conditions.