The Seven Halls, or Sette Sale, is the name of the complex of cisterns located on the Oppian Hill. Previously believed to be connected to Nero's Domus Aurea, they were later found to be a large cistern supplying the Baths of Trajan. The cisterns were fed by a branch of the Trajanic Aqueduct. Found beneath the complex were the remains of a grotto lined with slabs of marble belonging to the Domus Aurea. In the fourth century CE, a domus was built on top of the complex, likely from a building used to service the tank itself. In the Middle Ages, the northernmost chambers were used as catacombs.
The complex, still quite well preserved, is built into the side of the Oppian Hill, shaped to conform to the terrain. The cisterns comprise nine (not seven) parallel chambers. The name Seven Halls comes from the fact that, when the complex was noted in the mid-18th century, only seven chambers were recognized.
References:Linderhof is the smallest of the three palaces built by King Ludwig II of Bavaria and the only one which he lived to see completed.
Ludwig II, who was crowned king in 1864, began his building activities in 1867-1868 by redesigning his rooms in the Munich Residenz and laying the foundation stone of Neuschwanstein Castle. In 1868 he was already making his first plans for Linderhof. However, neither the palace modelled on Versailles that was to be sited on the floor of the valley nor the large Byzantine palace envisaged by Ludwig II were ever built.
Instead, the new building developed around the forester's house belonging to his father Maximilian II, which was located in the open space in front of the present palace and was used by the king when crown prince on hunting expeditions with his father.