Here are some mystery story ideas with unique or unconventional settings:

1. A murder mystery set on a space station orbiting Mars. The limited number of crew members and isolated environment create a claustrophobic atmosphere as the detective tries to solve the crime.

2. A whodunit that takes place entirely within a massive multiplayer virtual reality game. The detective must navigate both the game world and real world to uncover the killer's identity.

3. A mystery set in an underwater research facility at the bottom of the ocean. Strange occurrences and equipment malfunctions lead to suspicions of sabotage or something more sinister.

4. A locked-room mystery that occurs inside a time machine. The victim is found dead, but the killer seemingly vanished into a different time period.

5. A murder investigation at a remote Antarctic research station during the six-month polar night. The harsh environment and isolation add to the tension as the killer remains among them.

6. A mystery set in a massive arcology - a self-contained city within a single structure. The detective must navigate the various levels and subcultures to track down the culprit.

7. A whodunit aboard a generation ship traveling to a distant star system. With limited resources and no outside help, solving the crime is crucial for the ship's survival.

8. A mystery that unfolds in a secret underground bunker during a nuclear apocalypse. Paranoia and claustrophobia run high as the detective tries to maintain order.

9. A murder at a remote monastery high in the mountains, cut off from the outside world. Ancient traditions and vows of silence complicate the investigation.

10. A mystery set in a futuristic "smart city" where everything is automated and monitored. The detective must unravel how a crime was committed despite ubiquitous surveillance.

When crafting these unconventional mystery settings, focus on how the unique environment impacts the investigation and creates additional challenges or intrigue. Use the setting to add atmosphere and tension to the story. Be sure to establish the rules and limitations of the setting early on so readers can follow the logic of the mystery as it unfolds.