"The Lumière des Etoiles casino was an enormous building with tall columns and was topped by a vast glass dome. If it wasn't for the electric sign blinking its name, Conner would have thought it was an old town hall that had been painted a sandy yellow to match the rest of the city."
The (fictional) casino Lumière des Etoiles ("Starlight") is placed in Monte Carlo, Monaco. Under the casino lies a hidden storage facility. In A Grimm Warning, Conner, Bree and Granny Pearl travel there to retrieve the magic panpipe from Mother Goose's vault.
The casino has green marble floors and golden pillars lining the walls. It is filled with elderly patrons. While Conner and Bree access the secret bank, Granny Pearl stays in the casino area.
Conner and Bree hand a special poker chip to the roulette dealer of a gaming table in the northwest corner, and tell him they want to bet on black, like Mother Goose instructed Conner when she gave him the chip at the end of The Enchantress Returns. It is a sign they wish to enter the vault.
Mother Goose's vault is in the third-highest level of the sceret bank. The chip acts as a key to the vault. The manager of the bank explains that the storage rooms are not rented or leased but purchased in perpetuity, like cemetry plots.
The inside of Mother Goose's vault looks like the storage room of a museum.
"There were large Egyptian busts, small Fabergé eggs, hundreds of rolled-up scrolls, portraits, canvases, dinosaur bones, clay pots and pans, and even a giant machine gun from World War II."
Mother Goose has labeled the items. Some of them are rather peculiar ("George Washington's teeth", "Map to Atlantis", the "Holy Grail") but they eventually find the panpipe.