Answer: The Marina Green

Prior to the 1906 earthquake, the Marina was mostly marshland and dunes making it impossible to build on. After the earthquake, the area was used as a dumping ground for a good portion of the ruins and rubble that was left in the aftermath of the quake. When San Francisco was granted of honor of hosting the world’s fair in 1915, the Panama-Pacific International Exposition, the rock and rubble were transformed into an unstable foundation for the event. After the fair ended, the area was cleared out leaving only one of the main exposition buildings, the Palace of Fine Arts, as a sign that the fair had been there.