The Crystal Palace is the name given to Yamada Elf's house and work space. It is next-door to the Izumi House and gives one clear access to "The Never Opened Room". It is located in the city of Tokyo.
It was said that a great author, who wrote two well known novels called Old Mansion and The Girl in White, once lived in the house and died of illness. Afterwards, people considered the house haunted. Rumors stated that a piano sound came from the house along with a white ghost that wears a suit. Eventually, Elf buys the house and becomes neighbors with the Izumi siblings.
The house is two stories. On the outside there is a courtyard. Inside, there is a western style room that's about 10-tatami mats with a wooden floor covered in red patterns. Elf's study and office is on the second floor and is called "Office Moonside".
The wooden door has a golden handle and a nameplate that says "Office Moonside" and is right across from Sagiri's "Never Opened Room" with the windows being close enough for Masamune to jump from one room to the other. The room was made into a legal company for Elf's tax purposes.