One Shot: Moonstone Mask

[Wasum]

Hello everybody - I want to run a short adventure tonight as some of my players want to visit the Moonstone Mask in Neverwinter. The establishment is the center of organized crime people say but appears a quiet noble festhall on an earthmote. The session ought to be completed in a few hours I primarily want to introduce the Moonstone Mask a an extraordinary location with its own mystery and appeal that contrasts my pretty gritty Neverwinter setting.
The purpose for my players going there lies in investigating one players past but I want that to only be the hook and focus on the wounderous place.

First thing that came to my mind was the bathhouse in Spirited Away as a blueprint for a location that follows some otherworldly logic but I would really appreciate any kind of advice you might have: What happens there? What makes that place special? What will the players encounter there?

Thanks in advance:)

Wasum